The series 2a Swb was made from 1962-1972 I believe. The series 3 came out in 1972, however there were various incarnations of the 2a. General/transitional/late. On the general the headlights were on the central grill on transitional they moved to the wings and on late they were recessed into the wings like the series 3. As production of 2a finished and 3 began there were various discrepancies in models due I guess to stock being used up so late 2a’s often had series 3 parts fitted such as suspension, alternators, wiper motors etc. Later series 2a had a thicker bonnet, early ones had a thinner one more like the series 1. Series 1 were built from 1948-58 followed by series 2 58-61. The 88 is size of the rear area. Series 1 generally had a steeper angle windscreen and came in shorter sizes originally 80” 81”, 86” then 88” like the series 2/2a. Series 2 and 3 came in 88 and 109. Before the newer defender which was 90, 110 and 130. I think it’s likely your father was driving a series 1 but hope my descriptions help you
