I'm afraid I don't have any info on the Houlton, Maine manufacturing question.

That series of pistols includes the 622 and 422, both alloy frames, the 422 in a "blued" finish, and the 622 having a Stainless slide, and matching (more or less) anodized frame. There's also the 2206, which is completely stainless steel, and much heavier. Also a 2213 and 2214, more compact models, I'm afraid I forget the details of these models. And, I guess they all were more or less follow-ons to the original model 61.

I have a 2206, 2 x 422s (4 & 6 in.) and a 6 in. 622. I love them all, great shooters. I would love to add a 2213/2214 to the mix, also. The VR was, I believe, a rather limited production with the vent rib. Also, all models (eh...not sure about the 2213/2214) were built with fixed sights (well, drift adjustable rear sights, I believe) or with adjustable sights.