I had the original piranha, where the front grip was the air, and a front grip, or bottom line hose was a "mod", i later had an STS, and then i played with a buddy who had a decked out eblade autococker, and a chipped bob long defiant.
takes me back... good luck with sale, my piranha STS was fun, and reliable. PMI's Flush cocking didn't exist then, the STS had a beaver tail, and the original piranha,the cocking handle sometimes would clip you in the face, and chop, or double feed.