Kirby Hoyt at vintagedoubles.com had a gauge for sale that was less than $500, new. As he put it, "If it saves you buying one gun that isn't safe, you come out ahead financially." (And that's even if you don't find out the really hard way.) A number of people on this board, myself included, consider Kirby to be reasonably priced and honest. It would be a mistake not to contact him.