That was the very first plate out of the first laser cut production run (I had a place laser cut flat stock with outer shape and all slots...much easier and cost effective). It is production #10 since the first 9 were all 100% hand cut and hand made that I set up with harnesses and wings as beach test units. Anybody who was interested could show up to a scheduled test dive event and try one. Eventually they all found homes so I could finance more runs of plates.
That design you have was built around the first style Oxycheq wing which was wider and bigger than the current Mach V series. Then they quit making the old Signature and Razor series and went exclusively to the Mach V. I had to change the entire design to accommodate the wing since it seemed to be the number one single tank wing at the time, it may not be anymore? I don't know.
That's when #10 got a refit and change. There were originally slots above where the top slots are now, plus at the time I was trying out an idea of cutting big rectangular holes and welding a rail on so that the cam strap would recess down a bit. It was also an attempt to speed up production times. The waist slots were originally just cut out like other plates although at different angles to try and make the straps follow a more natural angle. I was also at the time trying something new with waist slots by cutting out the center and welding in a bar to make it a slider. It was also an attempt at less production time. Rounding over and smoothing narrow 1/4" slots from a razor sharp laser cut takes a lot of time and patience, The larger the access the easier it is, hence large square holes...but then there's welding...so it's a toss.
Anyway, that plate you have was refit a few times but I never intended to sell it. I used it for a few years before I came up with the new Contour series so then that took over. I always made a point of wearing my own latest and greatest so people would see them.
Old No. #10 is made out of 304 so you can use 316 316L or 308 filler rod, I don't think it'll matter much. I don't think the metals are dissimilar enough to matter. It's not going to live in salt water 24/7