Probably owned 30-40 of the corresponding boxing W519/520s, before I sold them. Only 2 or 3 had the Decalco mark (and they were not as complete as Leon's). So I would say that the mark was not between each card. Also being that the ones I saw were "cut", I have to think
that the mark was not at end of strip, but somewhere in the strip, between players.
Cool strips, wish I still owned them.