That was my thoughts also....but the cartouche appears to be the wrong shape for both the gothic "r" and the "t". Each of these date letters are shown as being in an oval cartouche.
As of course is the cartouche for the letter "r". The published examples of the Birmingham gothic date letter series show inconsistencies in outline, some rectangular, some oval. The suspicion must be that the punches for a particular year produced either shape.