Would love to see pix of the lock. Not familiar with Martin Sheetz of where he may have worked. Regardless, quality export locks, or locally made locks of the period ~1770 to 1809 would have had bridles, and also flys if intended for use with double set triggers. Cheaper, less quality locks, such as the locks commonly used on Trade Guns would have been more likely to be without bridles.
It’s not surprising that your lock internals resemble those of Chambers locks, since Chambers locks are all patterned after original examples.
Good luck with your build
Jeff