Unidentified 9x19 headstamp

I’m looking for the maker and country of origin for this 9x19 headstamp.
I only have this picture since 2001. Can anyone be of any help?

Lew C urtis showed this same headstamp some time ago asking for information on it. There were some theories, but I don’t recall anyone coming up with a positive explanation. Clearly, it is “S 3” and not “S B” as some has asked in the past. It is not the work of Sellier & Bellot. I think this only showed up in Spain, or on a Spanish website, anyway. I haven’t a clue what it is.