IIRC, the excursion switches were a way around a patent that Peavey held for a variable depth pot.
Peavey patented that? The 1st I saw depth control was on the SLO100. I tried it in my amp too but took it out to do something else with the pot. For the record the 1st 5150 made by Peavey was almost an exact copy of the SLO. Same with the Rectos. There’s a history of companies successfully patenting things that other people came up with. Randall Smith was a little infamous for doing that.