The F-1 rocket engine was not a single, off-the-shelf product; rather, the engine was constantly tweaked and its configuration frequently updated, either as the result of a customer request or a suggestion by the manufacturer to simplify construction or to address issues they encountered. Engine changes began as an "engineering change request (ECP)" and approved changes were implemented as an "MD change" (I've never seen an explicit explanation of what "MD" stood for, but I did read something which seemed to imply that it was "model designation").

Some changes were major configuration changes, while others were relatively minor. Some engines were originally manufactured after the change had been implemented and so the change was incorporated in the engine as it was shipped from the factory, while other engines were retrofitted with the change in the field. Other changes were not deemed important enough to warrant the expense of retrofitting engines.

Regardless of the source or magnitude of the change, it was necessary to keep track of which changes had been applied to which engines. In addition to the importance of good record-keeping (which, of course, NASA loved), installation and checkout procedures sometimes had to be updated as a result of specific engine modifications. Thus, it was necessary for technicians to know what MD changes had been incorporated in a particular engine.

To this end, engines bore an identification plate documenting which MD changes had been incorporated. As it turns out, during the F-1 production run, there were two different types of ID plates documenting MD changes (one wonders whether the change to the ID plate corresponded to an MD change!).

Click image for a 2019x1876 pixel version of this image in a new window.
From p. xvi of the F-1 Rocket Engine Technical Manual: Engine Data (R-3896-1), located in the archives of the U.S. Space & Rocket Center. Formerly available from the NASA Technical Reports Server.
Scan by heroicrelics.org.

The MD identification symbol and the equipment model designation indicated the configuration of the engine and distinguished it from models incorporating different changes and from basic models. A basic, unchanged configuration of the engine had no MD identification symbol. MD identification symbols were added as changes affecting configuration were incorporated. The MD identification symbol was stamped on the MD plate, which was mounted near the engine nameplate.

On MD identification plate RD171-1022-0001, above, the identification symbol was a composite number representing all the changes affecting configuration (MD changes) incorporated or not incorporated into the engine. The symbol represented a consecutively-numbered series of MD changes. Any MD change, or series of MD changes, not incorporated was represented by an "X." Multi-digit numbers were underlined. Two figures together represent the limits of a series of incorporated MD changes.

See F-1 engine F-4028 at the U.S. Space & Rocket Center for an example of an F-1 with the RD171-1022-0001 MD identification plate.

Click image for a 2019x1876 pixel version of this image in a new window.
From p. xvi of the F-1 Rocket Engine Technical Manual: Engine Data (R-3896-1), located in the archives of the U.S. Space & Rocket Center. Formerly available from the NASA Technical Reports Server.
Scan by heroicrelics.org.

MD identification plates RD171-1052-0001 through -0006, above, had pre-printed numbers from 1 through 100 on the -0001 plate, 101 through 200 on the -0002 plate, etc. Modifications that were incorporated into the engine were represented by the letter P (production) or K (kit) stamped in the square directly to the right of the applicable number. The lack of a P or K indicated that the MD change was not incorporated in the engine. A P or K with a bar marked through it (i.e., P, K) indicated that an MD change was deleted in its entirety by the incorporation of a later MD change.

See F-1 engine F-6045 at the U.S. Space & Rocket Center for an example of an F-1 with the RD171-1052-0001 MD identification plate.

Approved F-1 ECP Numbers and Corresponding MD numbers

Here's a table of approved F-1 engineering change proposal (ECP) numbers and their corresponding MD change numbers, as of 12 May 1972. The F-1 Rocket Engine Technical Manual: Engine Data (R-3896-1), which describes the F-1 rocket engine, had to be updated for many MD changes, and the table also lists the issue date of the manual which was updated for the MD change.

Approved ECP No.	MD No.	Incorporated in Manual Dated
F1-38	37	17 May 1965
F1-38R1	--	N/A
F1-39	11	8 June 1964
F1-40	--	N/A (superseded by F1-254)
F1-42	7	8 June 1964
F1-45	7	8 June 1964
F1-56	7	8 June 1964
F1-57	7	8 June 1964
F1-59	7	8 June 1964
F1-60	16	N/A
F1-62	7	8 June 1964
F1-64	7	N/A
F1-65	7	8 June 1964
F1-67	10	8 June 1964
F1-69	7	8 June 1964
F1-71	9	8 June 1964
F1-74	7	8 June 1964
F1-76	24	27 October 1964
F1-76R1	--	N/A
F1-78	7	8 June 1964
F1-80	7	8 June 1964
F1-82	18	8 June 1964
F1-85	7	8 June 1964
F1-86	7	8 June 1964
F1-90	7	8 June 1964
F1-91	7	N/A
F1-95	7	8 June 1964
F1-97	7	8 June 1964
F1-98	20	N/A (superseded by F1-197)
F1-99	14	8 June 1964
F1-100	7	8 June 1964
F1-101	8	8 June 1964
F1-106	7	8 June 1964
F1-108	7	8 June 1964
F1-124	7	8 June 1964
F1-129	8	N/A
F1-129R1	--	N/A
F1-131	7	N/A
F1-132	7	8 June 1964
F1-135	7	8 June 1964
F1-143	11	8 June 1964
F1-143R1	--	N/A
F1-146	1	8 June 1964
F1-147	7	8 June 1964
F1-149	11	27 October 1964
F1-153	7	N/A
F1-154	7	8 June 1964
F1-166	13	8 June 1964
F1-168	8	8 June 1964
F1-169	7	8 June 1964
F1-172	7	8 June 1964
F1-174	21	N/A
F1-174R1	--	N/A
F1-176	22	N/A
F1-180	34	27 October 1964
F1-182	7	N/A
F1-185	32	11 May 1964
F1-185R1	--	N/A
F1-188	7	27 October 1964
F1-188R1	--	N/A
F1-189	7	27 October 1964
F1-191	7	27 October 1964
F1-192	46	28 September 1965
F1-192R1	--	N/A
F1-192R2	--	N/A
F1-193	7	27 October 1964
F1-193R1	--	N/A
F1-194	7	27 October 1964
F1-195	7	27 October 1964
F1-196	29	N/A
F1-197	20	27 October 1964
F1-198	26	N/A
F1-198R1	--	N/A
F1-202	7	27 October 1964
F1-206	22,66	27 October 1964
F1-206R1	--	N/A
F1-206R2	--	N/A
F1-208	33	27 October 1964
F1-214	31	28 September 1965
F1-214R1	--	N/A
F1-215	116	8 August 1966
F1-215R1	--	N/A
F1-215R2	--	N/A
F1-216	31	N/A
F1-216R1	--	N/A
F1-217	7	N/A
F1-226	35	N/A
F1-228	36	27 October 1964
F1-229	8	27 October 1964
F1-229R1	--	N/A
F1-233	38	28 September 1964
F1-235	31	N/A
F1-236	7	27 October 1964
F1-241	7	27 October 1964
F1-242	39	27 October 1964
F1-244	7	27 October 1964
F1-251	7	27 October 1964
F1-253	43	N/A
F1-254	7	27 October 1964
F1-255	42,45	N/A
F1-258	22	27 October 1964
F1-258R1	--	N/A
F1-258R2	--	N/A
F1-260	54	N/A
F1-260R1	--	N/A
F1-260R2	155	N/A
F1-261	22	17 May 1965
F1-262	50	N/A
F1-263	51	N/A
F1-267	49	17 May 1965
F1-268	59	17 May 1965
F1-268R1	--	N/A
F1-269	55	17 May 1965
F1-270	47	28 September 1965
F1-270R1	--	N/A
F1-270R2	--	N/A
F1-274	53	N/A
F1-276	22	N/A
F1-277	61	N/A
F1-278	64	N/A
F1-279	21	N/A
F1-279R1	--	N/A
F1-282	31	12 January 1966
F1-283	65	14 October 1966
F1-283R1	--	N/A
F1-283R2	--	N/A
F1-285	68	28 September 1965
F1-285R1	--	N/A
F1-287	31	14 October 1966
F1-288	31	14 October 1966
F1-289	63	N/A
F1-289R1	--	N/A
F1-289R2	--	N/A
F1-294	57	17 May 1965
F1-294R1	--	N/A
F1-294R2	--	N/A
F1-303	54	8 August 1966
F1-303R1	--	N/A
F1-304	67	N/A
F1-304R1	--	N/A
F1-305	73	28 September 1965
F1-305R1	--	N/A
F1-306	66	N/A
F1-306R1	--	N/A
F1-306R2	--	N/A
F1-307	74	N/A
F1-307R1	--	N/A
F1-308	31	N/A
F1-309	77,80,95	8 August 1966
F1-310	78,80,95	8 August 1966
F1-311	31,108	28 September 1965
F1-311R1	--	N/A
F1-312	96,97	12 January 1966
F1-312R1	--	N/A
F1-312R2	--	N/A
F1-312R3	--	N/A
F1-312R4	179	N/A
F1-313	69	28 September 1965
F1-313R1	--	N/A
F1-314	31	28 September 1965
F1-315	70,83	28 September 1965
F1-315R1	--	N/A
F1-315R2	--	N/A
F1-316	31	8 August 1966
F1-317	71	8 August 1966
F1-319	31	N/A
F1-320	75	8 August 1966
F1-320R1	--	N/A
F1-321	31	28 September 1965
F1-323	84,85,86	N/A
F1-323R1	--	N/A
F1-323R2	--	N/A
F1-323R3	--	N/A
F1-324	72	28 September 1965
F1-324R1	--	N/A
F1-326	79,80,95	N/A
F1-328	76	28 September 1965
F1-328R1	--	N/A
F1-331	31	8 August 1966
F1-332	31	N/A
F1-333	54	8 August 1966
F1-335	31	31 March 1967
F1-342	30	N/A
F1-343	90,91	31 March 1967
F1-347	31	31 March 1967
F1-352	31	12 January 1966
F1-352R1	--	N/A
F1-353	82	N/A
F1-356	88,93	28 September 1965
F1-357	89	8 August 1966
F1-358	31	8 August 1966
F1-360	99	8 August 1966
F1-361	92	N/A
F1-362	54	31 March 1967
F1-369	94	8 August 1966
F1-370	106	N/A
F1-370R1	--	N/A
F1-370R2	--	N/A
F1-370R3	--	N/A
F1-370R4	--	N/A
F1-371	31	7 April 1966
F1-372	100	31 March 1967
F1-372R1	--	N/A
F1-372R2	--	N/A
F1-378	58	N/A
F1-378R1	--	N/A
F1-378R2	--	N/A
F1-378R3	--	N/A
F1-379	101	12 January 1966
F1-379R1	--	N/A
F1-379R2	--	N/A
F1-380	99	7 April 1966
F1-381	31	N/A
F1-391	102,103	7 April 1966
F1-391R1	--	N/A
F1-392	137	31 March 1967
F1-392R1	--	N/A
F1-392R2	--	N/A
F1-405	128	31 March 1967
F1-405R1	--	N/A
F1-405R2	--	N/A
F1-406	--	31 March 1967
F1-407	109	31 March 1967
F1-407R1	--	N/A
F1-408	104	7 April 1966
F1-408R1	--	7 April 1966
F1-409	105	7 April 1966
F1-410	128	31 March 1967
F1-410R1	--	N/A
F1-415	107	8 August 1966
F1-416	120	31 March 1967
F1-416R1	--	N/A
F1-417	--	N/A
F1-418	--	31 March 1967
F1-418R1	--	N/A
F1-419	--	31 March 1967
F1-419R1	--	N/A
F1-420	--	31 March 1967
F1-420R1	--	N/A
F1-421	--	N/A
F1-421R1	--	N/A
F1-421R2	--	N/A
F1-422	113,114	8 August 1966
F1-422R1	--	N/A
F1-423	119	N/A
F1-423R1	--	N/A
F1-424	110	8 August 1966
F1-424R1	--	N/A
F1-426	117	8 August 1966
F1-426R1	--	N/A
F1-427	111	31 March 1967
F1-427R1	--	N/A
F1-427R2	--	N/A
F1-428	87	N/A
F1-428R1	--	N/A
F1-430	112	8 August 1966
F1-431	137	31 March 1967
F1-431R1	--	N/A
F1-431R2	--	N/A
F1-432	125	31 March 1967
F1-432R1	--	N/A
F1-432R2	--	N/A
F1-434	121	31 March 1967
F1-434R1	--	N/A
F1-436	123	8 August 1966
F1-437	115	14 October 1966
F1-437R1	--	N/A
F1-437R2	--	N/A
F1-437R3	--	N/A
F1-438	131	31 March 1967
F1-439	146	10 August 1967
F1-439R1	--	N/A
F1-441	140	10 August 1967
F1-441R1	--	N/A
F1-441R2	--	N/A
F1-441R3	--	N/A
F1-443	129	14 October 1966
F1-444	139	10 August 1967
F1-444R1	--	N/A
F1-444R2	--	N/A
F1-445	122	8 August 1966
F1-445R1	--	N/A
F1-447	138	N/A
F1-447R1	--	N/A
F1-447R2	--	N/A
F1-448	149	10 August 1967
F1-448R1	--	N/A
F1-448R2	--	N/A
F1-449	127	31 March 1967
F1-449R1	--	N/A
F1-452	126	31 March 1967
F1-452R1	--	N/A
F1-453	123	N/A
F1-454	118	31 March 1967
F1-454R1	--	N/A
F1-454R2	--	N/A
F1-456	124	8 August 1966
F1-456R1	--	N/A
F1-457	136	N/A
F1-459	130	31 March 1967
F1-464	--	14 October 1966
F1-467	--	N/A
F1-467R1	--	N/A
F1-468	128	31 March 1967
F1-470	140	10 August 1967
F1-470R1	--	N/A
F1-470R2	--	N/A
F1-471	--	N/A
F1-475	--	N/A
F1-475R1	--	N/A
F1-475R2	--	N/A
F1-476	135	31 March 1967
F1-476R1	--	N/A
F1-478	137	N/A
F1-478R1	--	N/A
F1-478R2	--	N/A
F1-480	132	31 March 1967
F1-480R1	--	N/A
F1-482	133,134,142	31 March 1967
F1-482R1	142	10 August 1967
F1-495	144	10 August 1967
F1-495R1	--	N/A
F1-498	145	10 August 1967
F1-498R1	--	N/A
F1-498R2	--	N/A
F1-499	137	10 August 1967
F1-499R1	--	N/A
F1-500	150,151	10 August 1967
F1-500R1	--	N/A
F1-502	148	N/A
F1-504	141	31 March 1967
F1-504R1	141	10 August 1967
F1-505	161	N/A
F1-505R1	--	N/A
F1-505R2	--	N/A
F1-506	159	13 February 1968
F1-507	--	N/A
F1-509	143	N/A
F1-510	152	10 August 1967
F1-510R1	--	N/A
F1-511	146	10 August 1967
F1-511R1	--	N/A
F1-512	177	10 August 1967
F1-512R1	--	N/A
F1-515	147	14 July 1968
F1-515R1	--	N/A
F1-521	154	13 February 1968
F1-521R1	--	N/A
F1-521R2	154	11 March 1968
F1-521R3	--	N/A
F1-521R4	183	N/A
F1-522	--	N/A
F1-523	--	13 February 1968
F1-524	--	13 February 1968
F1-525	157,158	13 February 1968
F1-525R1	--	N/A
F1-526	156	14 July 1968
F1-526R1	--	N/A
F1-530	162,163	13 February 1968
F1-530R1	--	N/A
F1-530R2	--	N/A
F1-530R3	--	N/A
F1-535	--	N/A
F1-543	165	11 March 1968
F1-543R1	--	N/A
F1-545	154	11 March 1968
F1-547	169	N/A
F1-548	160	13 February 1968
F1-548R1	--	N/A
F1-552	170	14 July 1968
F1-552R1	--	N/A
F1-552R2	--	N/A
F1-579	--	11 March 1968
F1-580	--	N/A
F1-581	167,168	14 July 1968
F1-581R1	--	N/A
F1-581R2	--	N/A
F1-581R3	--	N/A
F1-581R4	--	N/A
F1-586	--	N/A
F1-587	--	N/A
F1-590	176	18 August 1969
F1-590R1	--	N/A
F1-590R2	--	N/A
F1-590R3	--	N/A
F1-590R4	--	N/A
F1-591	172	N/A
F1-592	173	18 August 1969
F1-592R1	--	N/A
F1-594	--	N/A
F1-594R1	--	N/A
F1-596	174	N/A
F1-596R1	--	N/A
F1-597	175	N/A
F1-601	--	N/A
F1-602	178	N/A
F1-604	180	4 November 1970
F1-607	181	4 November 1970
F1-607R1	--	N/A
F1-607R2	--	N/A
F1-607R3	--	N/A
F1-612	184,185	4 November 1970
F1-612R1	--	N/A
F1-612R2	--	N/A
F1-613	186,187	4 November 1970
F1-617	--	N/A
F1-618	188,189,190	N/A
F1-618R1	--	N/A

The bulk of the descriptive text was taken, largely verbatim, from F-1 Rocket Engine Technical Manual: Engine Data (R-3896-1).