Mike, it has the look of a transitional knife (except for the plates) but it is possible that there was no RZM mark - maker mark only. I think the RZM mark would be stamped rather than etched but I've never seen one from this maker, so can't be sure. The RZM number for Weltersbach is M7/22.
It's really difficult to try and 'box' some of these knives to a certain period. Russ has an example that is a transitional: Weltersbach maker marked, Ges. Gesch. RZM M7/22, motto and no ricasso. Here we have a maker only, I think most likely with motto, possibly with a worn off RZM mark, with ricasso, and using the often seen early stretch grip plates. It also appears to have an early steel hilt rather than zinc.
Sometimes, the logical manufacturing pattern doesn't seem to be what we think it should be.
I also agree that the bowie shape was likely not done by the manufacturer.
Regards
Russ