1952 was the year they started putting the serial numbers on the left drop-out, so yours has to be before that. Unfortunately all the records before 1948 were lost in a fire. They were using serials starting with I, J and K during the war, and started over with A serials sometime in the early post-war period, but there's also other numbers that show up that don't really fit the sequence, even in the lists that survive, so it comes down to judgement in the end. But your bike can't be 1952, and 1948 fits the features you have, so that's your best bet. There's a couple of threads on the DX model, looking at other examples may help.
Good luck with your wheel!