I have two pair. One pair is marked 916 on each panel. The other pair is marked 1064 on each panel. I choose to believe these are order numbers/customer numbers. I choose to believe any/all grips without a number (of 1,2,3,4, possibly 5 digits) on each panel are those produced before they started to number them. I choose to believe any frame size markings were placed there by an owner. I choose to believe any brand marking (S&W, Colt, etc.) were placed there by an owner.
Bottom line of what I choose to believe is I choose to believe any markings which would likely prove to be helpful in the operation of a grip making business were placed there by the folks in the grip making business---and any other markings were placed there by somebody else.
As an aside I believe I can prove to pretty much anyone's satisfaction any caliber markings were placed there by an owner-----prove it with Roper's own words (from his writings) where he essentially ridicules the consideration of caliber in the design of grips.
Time to eat------------
Ralph Tremaine