Well, I actually got the NOS one before (in fact it was my 3rd mercury lamp ) but I've only run it a few times. This one was a Restore find but it's probably only slightly used.
The BT bulb the 700w lamps use are similar to the BT-37 and the BT-56 too. I think fake Westy also used to have a BT-28 that looked like a shrunken BT-37. Oh and I think the BT-15 bulbs used by halogen lamps look more like mini BT-37 bulbs too.
Not sure why they haave different BT styles though.
So you bought another merc lamp huh? What size/phosphor?
Not sure why they haave different BT styles though.