Lock screw question

[B52]

Some years ago I found this poppet-type lock screw in a junk box at a gun show. It has about 50% of a dark finish remaining, but it has no markings whatsoever, not even a punch mark. It looks like the one I've seen in photos of the non-returning valve type with carbon steel spring. It functions, however, like a normal self-closing spring type. I can only think of two explanations. First, that it is an early or prototype self-closing valve type made by SA; second, that it began life as a non-returning spring type, but was converted to the later type, if that's possible. Any insight will be greatly appreciated.

Thanks,
Kevin

[CPC]

Post a couple pictures and the experts will be able to tell what it is. I doubt it is a prototype as I suspect it would have been marked in some way to indicate it was a poppet valve. I am not sure if an early valve can be converted to a standard valve, but I think it could be as I believe the hole may be a little bigger and easily enlarged, but then again I would suspect that it would have been marked/stamped. According to Bill Ricca on his site it is believed that some of the early carbon steel springs were upgraded to stainless steel and even these were hand stamped to reflect the new spring with an S. I have variations of the S stamped early valves in my collection, both rolled and hand stamped, serif and non-serif. Maybe the spring is just worn in yours and it does not stay open. By looking in the valve you can easily tell if it is the early type. If it is a poppet valve it was most likely very lightly stamped which I have had before and had to look at under a glass; or it was polished off and refinished (not sure why but I've seen those too), or it just may have been a manufacturing error and the stamp broke or lock screw turned in the belt/etc when running through the machine etc and did not get stamped. Since millions were made I doubt it is a rare anomaly. hopefully someone with real knowledge will comment to help you out.