He asked "What would be the issue holster for a 1934 Enfield No2 MkI Revolver in .38-200 and what would be the most likely used holster in WWII for the same revolver".
I assume this to be 'what would it have been issued with' AND 'what would be the most likely in WW2'
So I would think, '25 pttn until the '37 pttn became mainstream. I believe the RAF used '25 pttn for many years after the intro of '37 and well into WW2.