So far i got: UG ten book distinguishes V1 thin crown for MK1 and V2 thick for later MK1 / MK2.
The V1 thin measures 6.1mm in diameter and thickness of 2.9mm.
I think the Clapton MK1 crown V1 thin crown is identical.
Watch tube 2.5mm and Stem 1.2mm all the same
Anyone knows the measurements for the V2 thick ? looks much thicker.