Jim, that pistol doesn't appear to be a springer, CO2, or PCP, for sure: and in my opinion, it probably wouldn't qualify as an SSP either. It looks like a Multi (vs. Single) Stroke Pneumatic: aka a "pump-up".
Main comp doesn't have any categories for same.
However, my recommendation (just so, not a binding decision) is that because it's akin to an SSP, and because it doesn't offer any advantages over an SSP (probably the other way around, actually), it should be permitted in the SSP category.
Jim