My 639 was a mistreated example. Someone tried to install a set of Millet target sights for a 1911. The front sight is "stake-on" design and the tool won't fit the 639 slide. Took it to a good 'smith who welded up the holes in the slide and cut standard dovetail. Fitted the Millet rear and a fiber-optic front. Cleaned up the action while he had it too. Got this as part of a package: a pre 10 (4" about '49) and the 639 for $400. The 639 has proven to be a solid performer.