Two bob when I joined in 57. Unforgettable day. The officer administering the Oath was a retired Welsh Guards Colonel RO1 with a speech impediment, which meant that esses came squelching out from behind his teeth like the Welsh double 'L' sound. For those old enough, Dick Emery the comedian used to do a geezer with the same impediment. There were four of us being attested and we were nearly in bits when it came to "Her Majesty Queen Elizabeth the Second, her heirs and successors....." Lot of esses in there! We finally burst when paying us the aforementioned two bob he said to me, "Do you mind if it's all in sixpences?"
Didn't do him any harm though. Twenty-some years later, not long after I came out, I spotted the old Colonel when he was interviewed on telly when he finally retired from running the Royal Mews for the previous 20 years.