The # on the bottom of the frame visible with the gun all assembled is the ser#of course.

The # on the loading gate itself that you can see when you flip it open is an assembly # that was applied during original mgfr.
There should be a matching assembly # to this one on the bottom of the frame that you can only see if you remove the trigger guard.
These matching #'s applied to match the gate to the frame which were fitted and polished as one unit .
These were applied before the gun was ser#d, so it's a lotterys chance that the gate and frame assembly # would match the guns ser# stamped later in production.

All that said,,
They have nothing to do with re-work #'s stamped on various parts of the gun by the Colt service dept.
These are separate #s applied to the cyl, backstrap, triggerguard, bbl and frame,,sometimes the ejector rod housing. All or some of these parts were stamped depending on the work being performed when a gun was returned to Colt.

Your revolver has a # different from the guns ser# stamped on the cyl, triggerguard and backstrap (the latter is along the lower edge of the grip frame on the left side and is visable in the picture also showing the # on the trigger guard). These could those repair #'s.,,could be..

If the frame were to be stamped with a repair assembly #, it would be on the frame in the concave loading cut exposed when the loading gate is in the open position.
You'll also be looking at the gate assembly# described above at the same time, but they are unrelated and will not match.

The bbl was sometimes stamped on the surface covered by the ejector rod housing. The ejector rod housing sometimes stamped on it's concave underside.

All this done to keep track of the parts for a gun where extensive work and sometimes modification was being done. The part(s) may be gone from the service dept for a time to perhaps the machine shop or other specialty. The assembly# was unique, like a work order# and would avoid 'What's this go to?' and other mysterys.