The font for the property marking and model ID do match a 1945 Colt that I have. The SN on mine is cut slightly deeper, so polishing that off and not the other marks would leave a noticeable depression in the metal.
They very much match the 1943 Colts that I have; due to the G marking on the frame that was fortunately NOT ground off, I would guess that frame started life as a commercial frame that was remarked and pressed into service. It's a shame this gun was defaced, as it would have been worth a lot more given how infrequently a G marked frame comes up in USGI M1911A1s. I would guess that frame was ripped from the commercial line and probably repurposed around 1942?
Having close ups of the sides of the trigger guards, the rear of the frame where the crossed cannons would be, and by the mag catch where the acceptance cartouche and P proof mark would be, would be helpful too. Those grips are much larger than the as-issued ones and might need to come off to see all the markings.
The M1911A1 US ARMY and USP markings are much, much deeper than the 3 samples I have here which is what lead me to believe that whomever ground the frame down remarked them, very deeply, so they wouldn't be ground off. It could also be a trick of perspective...the dishing around the letters from the overpolishing could also make it look a little distorted and deeper than they really are..
Edit - the markings also match my 1944 Colt...the M1911A1 US ARMY font style is very specific to Colt on this one. I don't have a Singer to compare it to, but I do have a very early Ithaca (sub one million) a very late Ithaca (2.6+ million), and a Remington-Rand somewhere in the middle, and the M1911A1 US ARMY marking does not match any of those.