fwiw, I had a SF Deluxe Reverb that came to me with two single-button foot-switches. One with a 1/4" jack, and one with a home-made single RCA jack.
The one looked like the 1/4" foot-switch used on some other Fender amp (someone didn't have the correct footswitch, but said... "Yeah, I can make this work... lookit mey, Ah'm some kinda Janeious"
If I were seriously interested I would "ask the seller...".
On the other hand, let's hope it's a Pre=amp Tap!