Guy, this is a mis-matched gun, at some point the top and bottom halfs were mixed. The top part is a police period, i.e. in approx., 1933 the police decided to put in the sear safety and the mag safety.
But since the top part does not match the bottom part, all the collector value is gone,
My brother has a 1940 / 42 that I gave him, same problem as the one you are looking at. I have seen this several times, my guess is that some GI's were sitting around cleaning their weapons and just put parts back together. American pistols, well the top and bottom of a 1911A1 don't have matching numbers...
Ed