I've got a matching factory 'N' frame set that I've had for several years and I believe (not positive) they came off either a Mdl. 28 or Mdl. 29 that I once had and they look like the ones pictured below.
The checkering is excellent, the screw is included, they're not all scratched up and I'd rate them easily at 95%...inside one of the grips is stamped 'July 22, 1985'.
I haven't taken the time to see what they are worth but if you're interested shoot me a PM and we'll see if we can't work something out.