Each take is numbered, and a code is written next to the number. They include "FS" "PB" "INC" "HT" and "M". I'm thinking "FS" stands for "false start", "INC" stands for incomplete, and "M" means master, as in master take. What do these others mean?
PB = Playback. Usually refers to a dub or bounce-down from one tape to another.
AME is Ampex Master Equalisation, a board fitted as standard to Ampex tape machines. NAB is the Association of North American Broadcasters, who developed their own, superior, system of tape equalisation. (The other common one is CCIR, also known as IEC, which was developed in Europe.)