Mk III* (no cutoff) forends with the 'bulge' are found on rifles at least until 1918. Sometime shortly after WW1 the forend copying jigs were modified to create the straight contour. However, during the interwar period the cutoff was reintroduced and MkIII forends with provision for cutoff and with a straight contour were manufactured. I believe the 'shed load' of spare forends were manufactured to fit any mark of SMLE cutoff or no cutoff
