I think it is very hard to find 1911's chambered in .357 Sig, I definitely remember that Sig had planned to offer one but I lost interest in Sig guns, especially 1911's, so I quit paying attention.
Now then, Amati: obviously, the Coonan in .357 Magnum is far different than a .357 Sig chambered pistol, it is a little off track in this thread. I have one and LOVE it, but I don't think anyone needs to spend $2,000 on one or $1,500 on a used one unless it comes with a handful of magazines. I also don't agree that they are hard to get, there are scads of them on Gunbroker. The ones with the wacky finishes certainly cost more but IMO, those finishes take away from the fantastic pistols.
In any case, I want to know more about a "Nygord 52". I have and very much love Model 52's, are you talking about a custom 52? Can you tell us more?