If it is off a B-17 or for that matter B-24, C-47 etc – the prop is a Hamilton Standard 23E50 “Hydromatic” prop. The DH part number for the identical prop was 23EX; the primary difference was in the splines on the prop shaft. Lancasters, Mosquitoes and Beaufighters were fitted with the DH licence built version.

Incidentally, “Hydromatic” was a Ham Std patented name.