Old school Porta-keg, I think they are around 10L to 15L from memory. It has all connections for pinlock commercial setups, although will need all rubber o-rings replaced as they are in poor condition.
I ended up selling this one to someone on gumtree, got given it off my old man as he knew I was into beers and kegging. I have a bunch of party setups with ball lock posts so didn’t even bother with it.