A treble-and-bass tone stack placed directly in the signal path, without a dedicated cathode follower ahead of it, is the blackface arrangement. Two interacting controls scoop the midrange in the familiar Fender way; the stage feeding it simply absorbs the network's insertion loss rather than buffering it.
Dropping the cathode follower keeps the circuit simpler and the voice cleaner and more open than the follower-driven FMV stack used on the lead amps — one reason the blackface amps read as chimey and articulate where the British circuits read as thick and aggressive. It is the classic clean-platform tone.
The corpus places it between the buffered stacks above and the plainer single tone control of the small tweeds, so the whole ladder of tone-shaping choices is visible in one place.