By the way what are you looking for? A VAX or a SPARCstation? VAXes are indeed very hard to come by, and I didn't realise they were ever the "reference unix box" - weren't they more common for VMS? But somehow I never came across them back in the day. I think part of the reason is that they mainly sold servers, they weren't that big on the workstation market.
Sun, SGI and HP-UX I used a lot, HP-UX the most. I still have two HP-UX workstations at home.