Divided spring-loaded frames depicted in your thumbnail probably date 1928-1940. Before 1928, printing-out frames were adapted for darkroom use, after 1939, England was at war and photographic supplies were difficult to obtain throughout the Commonwealth. Look at the glass from the side. If it is green, it means nothing (replacement window glass), but if it is white (colorless) without striations or air bubbles, then it may be Waterford and probably original (unlikely) in which case, I would peg the date circa 1935. They are well used, do the same.
Originally Posted by Sean