The plate of the scabbard is from Vindonissa but I don't know exactly the datation.Martin your reproduction is really lovely!
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the Gemllianus scabbards may start in the late 2nd century AD, certainly in the 3rd. For a detailed discussion of the dating and lots of detail pictures and drawings etc. see:
Berger, Ludwig. Durchbrochene Messerfutteral-Beschläge (Thekenbeschläge) aus Augusta Raurica. Ein Beitrag zur provinzial-römischen Ornamentik. Forschungen in Augst 32, 2002.
These ornaments are quite frequent in the 3rd century. Sadly, we don't know, if they survived into the 4th century, or how they were attached (the 2 rings-on one side thing is speculation).