If it's not in your instructions, then you've got the wrong instructions....probably the ones for the original Eagle.
The Eagle II SL 90 Basic Users manual lists the preset starting programs on the very first page;
CJ = Coin & Jewelry, PP = Prospecting & Relic, bh = Beach Hunting, and ch=competition hunting.
Along with the Basic Users manual, there was also an Advanced manual.
Try to find both. There are a lot of hidden features in the SL 90, and it was one of my favorite detectors back in the day.
I've still got one black Eagle II SL 90, and one of the older blue Eagle II, and have fitted them with C to AA adapters for the power packs.
(It helps a little with the weight, and the newer NiMH AA's actually have more capacity then the original NiCad C cells had.)
Congrats on you acquisition, have fun, and good luck hunting!
mike
PS - And yes, White's did a really nice thing by printing most of the critical info on the control box....We could use more of that today.