Classic army scar-h hop up.
 

just wondering if anyone knows if the hop up is proprietary or if an aftermarket one is available?

As far as I am aware, the only ones that have a proprietary hop hup is VFC, I could be wrong though, easiest way to find out is to just pull it out of the gun and compare it to a standard one, if anything it's a standard V2 hop up.

I have one I'll check and see