The one on the left is earlier in the '50s, the one on the right from the end of the decade. As well as the points you note, like the serial number, the key is how the numbers are orientated in the registers.

The one on the left has them just as they were in the '40s. But if you look closely at the 3336 and 2444 in this 1961 catalogue:

you'll see that they too have them orientated as per your recent example. It's interesting to see the progression. Kind of like having an 1153 with 3-6-9-12 and single markers on a charcoal dial and another with 1-2-3-4...12 and double markers on deep blue, although the differences are maybe more marked between the A&Fs.

Worth putting up on OTD in my opinion, both as solo shots of the new arrival and that comparison.