I remember seeing this bell when it was listed on eBay several months ago and advertised as a Queen Mary Quarterdeck or Signal bell. Beyond that, I know nothing about it.
Using your new picture, it seems to me as if there is the beginning of the descender stroke in the R. The right side of the crown also looks more shallow than the left. If so, there might have been a casting flaw.
The Queen Elizabeth was delivered in 1938 and referred to Elizabeth, then Queen Consort and later Queen Mother of the current queen Elizabeth II. Yet, if 6/53 is a date, then it might point to the current queen and not the liner.
The Cunard Line operated both vessals. You might try to contact them and see if they have any information. http://www.cunard.com/