replenishing coupling on under side of the LOX replenishing coupling balcony.
The launcher table had a fitting which connected to this coupling to top off
the LOX tank.
The LOX replenishing coupling balcony on the tactical missile had a breather system
opening, used to circulate air in the tail unit if it was stored for any
length of time. It would seem either that they didn't plan on storing the
Project Mercury boosters for long periods of time or that they came up with a
better method of preventing condensation in the tail unit during storage.