Howdy
The number on the loading gate is just an assembly number. Has nothing to do with the SN.
However, according to my books, 65088SA would was built in 1973, making it a late 2nd Gen. Serial Numbers for 1973 ran from 64,401SA to 69,400SA with 4,999 produced that year.
I have one with the SN 647XXSA, which I had lettered a few years ago, and it was produced in January of 1973. Pretty darn close to the OP's 2nd Gen SAA.
The 3rd Gen started in 1976 with SN 80,000SA.