It's a shell by pchrisbosh1, from a few years back. I had that thing in a closet for close to three years while I waited for the remaining parts to arrive. I don't think he makes them anymore.
Took some pics lately with my new camera, thought I'd share them with you guys. The weathering is really subtle (to replicate the on-screen look of Venkman's pack in GB1, especially in the Sedgewick scenes) and it didn't show all that well in the last pics; I think it looks better now. Since I don't have access to a studio or to a professional photographer, it's kinda hard to show off all the details and hard work that's been put on that thing (Nearly 5 years in the making! Well, to be honest, I had to wait 3 years for some parts from a deadbeat seller, but at least it gave me the time to identify and locate pretty much every single vintage greeblie) I wouldn't go as far as to call it the most accurate version of the GB1 Venkman pack ever built or something, but in my humble opinion it's pretty spot-on (Aside from the top left mounting bolt. I know it's not in the right hole )