So the peltier cooled PMT has a really nice machined house, complete with lens and padding.
It has a potted voltage divider base, and the tube is heat shrunk with a bare wire down the side soldered directly to a pmt pin - I bet it's painted with conductive paint, as is common for negative HV operation, so I guess I also have a complete -HV PMT to compare with!
I'm considering using this one for either a plastic scintillator, or a Cherenkov detector, either a tank of water or a paddle of acrylic.
Figuring out if it's -HV or +HV should be as easy as measuring the resistance between the anode and BNC output - if it's +HV it should be AC coupled.
The pmt is a Hamamatsu R268HA, which is NOT an IR sensitive PMT as I initially thought. These are usually the ones that need cooling, but this one has been used in conjunction with a heater to heat up LiF crystal dosimeters, so it's probably just to avoid radiant heating of the PMT.
It also had a very intense blue filter which is probably also to block IR.