some time back I was in the habit of spending much time on the Replacements sites - but discovered it was a sure fire way of getting headaches - those places can have you staring at the screen for hours - and even then you don't always get an id.
Yes, I did look up the mark to see which years, and I'm tempted to think that for designs from those earlier periods there is perhaps less of a chance of finding a match - the site images tend to be of more recent patterns, say post 1950.
Subsequent to this period, W/Corbet did make the job easier for us by providing indications for either the exact year, or within a very close range. Upper case S or T apparently indicated Stourbridge or Tutbury in the late 1940's, and following on from that a star was used for both factories between 1949 and 52. After this you will find the actual year shown within the backstamp, starting with 52, and going on to at least 64, although Roger Dodsworth - 'Brit. Glass Between the Wars' - seems to suggest year dates ceased in 59 but I've certainly had one showing 64.