For what it's worth, I've got a Harrington & Richardson single-shot shotgun. This is one of the 'fancy' singles with a full length matted rib, checkering and pistol grip cap, dating, I think from sometime during the inter-war years. When I first acquired it, I thought there was something weird about the checkering, the panels seemed "fuzzy" or something. I finally realized there was no border around the panels of checkering. The grooves just ended beyond the last perpendicular cut. Mostly pretty even, though, with very few over-runs. Must have taken some practice.
I've always wondered why the gun makers didn't/couldn't think up a reason to sell guns with uncheckered stocks as some kind advantage. I've never really found uncheckered stocks that much of a disadvantage (if any) in actual use.
