Dave,
Yes I have but it was mostly on later 18th century guns that either had a replacement lock, replaced stock or was a cheaper end gun of same vintage using an older lock. The last one that comes to mind was a half stocked, c1780's waterfowling gun utilizing a 1720's era lock IIRC.
I can dig you out some pictures when I can get to my PC but I cannot remember many higher end guns made that way when the round face was very popular. I believe the flatter plates had taken the lead by the time the checkering was coming in with any authority. I would think the most would be found right at very late third quarter or beginning fourth.
As Taylor pointed out you can refer to Flintlock Fowlers. Although that Grinslade book only contains about 4 English guns, there is a big duck gun in there on page 171 with a round lock marked Wilson and the early lines on the wrist. I personally think it is a little bit later than the c1760 estimate given.
I have heard a few others throw out a 1760 time frame for early checkering. I tend to lean about ten years later with what I've seen to date but am willing to have my opinion changed. Just have not seen enough to suit me yet. Would be interested in your opinion as well.
James
PS. Just rememberd one Keith Neal owned that had a Grice marked lock on it. Will try and locate a pic as well.