The P2 is from 1996 and is made for a 13cm head tube (Kona size 19), although there is enough thread there for it to be cut down for an 11cm tube (Kona size 17 or 18 ). If it came off a Lava Dome or higher, it's triple-butted and should weigh c800g.
Are you sure that isn't an Impact? It looks like one and I didn't know anybody else made headsets that do up like that. The 1996 models with triple-butted P2s also had Impacts.