I stirred the pudding into a mess calling it an OP, however, as it's far more likely it would have been a shortened Army Special, which as you know--but our dear readers may not--was simply the earlier name used by Colt for the Official Police when it debuted in 1907 (if memory serves).  Around 1926 (again, pulling this out of the hat, my memory is shaky and I'm too busy or perhaps top lazy to look it up), Colt decided that the days of them selling revolvers to the military were over and they slapped the name "Official Police" on the good 'ol Army Special.  No doubt some of these AS revolvers were in inventory, however, and it wouldn't surprise me a bit if an Army armorer cut one down for a General officer.

I do think my assumption would carry more water if the big pistol were actually an M1911 rather than an M1911A1, taking us further back into the era when an AS revolver would likely to be found somewhere in an Army TOE, but even so, by the mid-to-late 1920s, a general would have the latest version of our primary pistol for the asking.

All this is based on my assumption based on photo perspective, however, and I could be sooooo wrong.