627-0 had "357 S&W magnum model of 1989" roll stamped on the right side of the barrel, a bigger cylinder stop notch, unfluted cylinder, checkered top strap, chromed hammer and trigger, only 5000 were made.
The no dash I believe did not have the "model of 1989" on the barrel, and did not have an unfluted cylinder standard (all of them I think). Not sure about how many of these were made.
The 627-1 had a tapped barrel and they discontinued the chromed trigger and hammer and "model of 1989" roll mark and I think they discontinued the fully checkered topstrap. I think the cylinder was fluted, but unfluted was optional.
Maybe I should have said "engineering revision" rather than "different model"