This is my late December, 1963 Fender Bassman 2x12. Its the 6G6-B circuit and was one of the early "tuxedo blondes" with the black faceplate, raised Fender logo and wheat grill cloth. The speakers are Oxford 12M6. Paul's blonde Bassman was an early 64, with Oxfords... which he probably got from one of the 2 UK Fender distributors. He used the amp from 1965 to late 68/early 69 when Don Randall of Fender got him the silverface AC568 Bassman with the 2x15 cab. That is the amp which is in the Get Back sessions and on Abbey Road. However the blonde Bassman, was used on more Beatles bass tracks (and a lot of guitar too) than any other amp. Paul played the guitar solo from Taxman on it, and the lead guitar on Paperback Writer too. Its a great amp and is very versatile.
Pete Townshend used an early 64 blonde on the Who's My Generation album and in their early shows. He said in an interview that he took it from John Entwistle and started using it for guitar.
According to Geoff Emerick they started using a DI for Pauls bass as well, just before the Paperback Writer session but they did not like it very much as it did not pull out the deep bass that they heard on American records, like Motown. So he rigged up a setup using a speaker as a microphone, for that session and it worked... got a huge bass sound. You hear a lot of the "cabinet" sound in the mid 60s Beatles tracks. Here is a photo from the Sgt. Pepper session where they have what looks like a U67 hanging out in front. Paul usually had the amp behind a baffle right next to Ringo's kit. The amp later made its way in to John Lennons office at Apple, then to John's home studio where it was used on the Imagine sessions and can be seen in videos from those sessions. It would be interesting to find out where it is now.
The Boulevard Recording channel on YT does a great job breaking down the Beatles recording techniques. Clay refers to the Bassman as a "62" but his is actually a 64 as well, due to the raised logo, black faceplate and wheat grill.