I was searching all over the net for any info and found the Webley Archive site. With this info:
(1) Mark III .38 Revolvers (1925 – 1929), numbers 27800 – 32899
(2) Mark III .38 revolvers (1929-1933) numbers 32900 – 39999
also Mark IV revolvers (1929- 1939) numbers 40000 – 42999
(3) Mark IV .38 revolvers (1940- 1941) numbers 43000 – 49999
also Mark III revolvers (1933- 1937) numbers 50000 – 53499 (53305 is mine) so maybe 1937.
(4) Mark III revolvers (1937- 1948) numbers 53500- 56479)
also Mark IV revolvers (1941- 1942) numbers 60000- 63799
Beerhunter. If you have reloaded these, I have just a couple questions.