Although they operate at 6.59 kHz like the other Classic models (and the XLT and XL pro and Quantums and many others), they differ from the Classic III SL, Classic ID, Classic IDX & IDX Pro in that they do NOT share the same set of search coils. All the others use the modern Blue Max series of coils, but the Classic II SL doesn't. Just a bit of difference in the "front end" electronic design and that means I'm sort of stuck using the stock 8" search coil.
On the bright side, the Classic II SL (like any of the decal/paint job variants) works. Plain-and-simple, the Classic II's work just fine. Several years ago my brother, Ed, wanted to get a detector to serve his needs. they were quite simple, too. He wanted a light and well balanced detector that would do a good job of just rejecting typical iron nails around homesteads, ghost towns and similar sites. He was only going to use the detector for those types of old, out-of-the-way locations and then just to pluck a lot of change from the urban wood-chip and sand-filled playgrounds.
All he needed was a Classic II. He didn't want Target ID so the Classic ID or IDX Pro were out, and he didn't want a large search coil, just a 'basic' detector w/8" coil and reliable performance. Well, I told him the Classic II came with an 8" coil and was about as 'reliable" as you could get. It served him well. He passed away in June and it's mine now ... and I won't part with it, either. It works!
Monte