Well, as a collector AND shooter,,, I kinda watch things.
To a collector of a certain model, say 44 mag NM's, a distributor special in that caliber will attract them to spend their money. To a "general" collector, it may attract them if it's an odd, low production variation, in something not often seen,,, such as the Vaqueros done in the 90's with the engraved & gold inlaid cylinders.
Next,, a lot depends upon the distributor offering,,, & how popular it is for the shooting public. Such as the 44 specials, done originally by Lipseys, that later became a catalog item.
To a collector,,, what we look for are the oddities that are in low production numbers, and desirable to many.
But it can be like trying to play the stock market.
How to track them?
Get a dealer who deals with XYZ distributor & become good friends. They are the ones who give us the production numbers & all the details on any exclusives.
As for the Williams guns,,,, not so much a collectable as a very desirable shooter by the masses.