Every 1911 I have seen from USFA (early on @ the SHOT show and on GB more recently) was a Caspian frame and slide.
I suspect Caspian would make anything you ask for if you are willing to write the check. I (have) had custom designed 1911 parts made in small batches many times (not small checks). Frames and slides are easy and cheap by comparison from Caspain, as are sights, hammers, triggers, thumb and grip safeties from others. There is a in depth, although small in number, cottage industry of machine shops that do such work for the Industry on both coasts.
Quick look at Caspian's web site shows a 1911 frame...without the 1911A1 trigger guard cuts as a normal catalog item. Been there for years now. And what the Turnbull/USFA guns were built on. No hiding that fact no matter what name is on the frame. With the right FFL license Caspian will put what ever it says on the frame. As an example I have a forged frame that I like to build on that has 4 DIFFERENT manufactures name on them...all made in the same place, by the same hands. In this case I'd buy a new production 1911 Colt or even an original Colt from BITD instead. It is a much better value IMO.
I saw a WWI Colt reproduction for under $1500 at the last WAC show. That is a decent price I think for a LOT more gun than the Turnbull on GB.
Caspain 1911 frame web page:
https://www.caspianarms.com/receiver/classic-receiver-carbonoriginal 1911 on GB now:
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=500028569Below is a recent build I did along those lines. Doesn't look like much really past the engraving by J. Adams Sr. Checkered ivory by Gunner Products. Colt 1911A1, aka modern frame cuts, older, small 1911 sights, slide release, grip safety and thumb safety. Only parts not OEM Colt are my ignition system and a friends old style hammer profile. (which is made by my hammer/internals maker from the same steel and specs I specify).
Doesn't look like much but in fact 1911s of any date don't get much better. It has always been the detailing that made any 1911 stand apart from the next. (or SAA for that matter) This gun was put together from pieces each specifically hand picked and over size
to hand fit. Then shot to make sure it was as good as hoped. Just as they did the early 1920's NM guns @ Colt. All that long before ivory or engraving.