I'd agree that they could be N frames for the snubbed 25-2's they used to build.

Or the only other idea I'd have is...could they possibly be a sort of stock sight they used on Auto's?

Austin did fit K frame adjustables to both 1911 and BHP's 40 years back. Later on I visited the shop and saw he had a different sight on a 1911 he had "Bobcatted' or shortened.

Behlert did a Colt Commander for me in the early 1970's. Armalloy finish, K frame adjustable rear, red ramp frt, action job, fitted Bar-Sto .45 match bbl, extended safety, long trigger. It ran like a top.

He wasn't cheap , or too awfully quick with delivery, but his work was top notch.

FN in MT