Three images of a cup and the marks on it. Clearly Birmingham marks, the date letter may be 1913, but is there a later series it matches?
I think I can persuade myself the maker's mark is A J Zimmerman used from 1913 onwards, though it is very unclear. what do more knowledgeable people think?
Hi and welcome to the forum. That is definitely a mark of A & J Zimmerman Ltd and it's most likely 1913. I have not found a way of distinguishing between the 1913 "o" and the 1938 "O" but Zimmermans went into liquidation in 1929. However I believe that whoever took the company over may have continued to use at least this version of their mark as I have seen it with dates up to 1940. So 1938 is still a possibility.
Don't rely on my representations of the date letters - they are indicative only. Compare some actual hallmarks and see if you can decide how they differ:
1913:
1938:
And remember that for each year there were a number of punches created which might not all have been exactly the same.