The other Coinmaster Classic series were okay, but when they brought out the Coinmaster III Plus, what a difference!
It offered the full-range Discrimination thanks to the Normal/Black Sand toggle selector, and also the change in search coils selection as it used the Blue Max series and the others used the older-type search coils. That added the the versatility of the detector a lot.
The next change was to drop the 'Coinmaster' name, calling them just the 'Classic', and also a change in the battery power and control housing and rod lay-out. The Coinmaster Classic III Plus is virtually identical in function and performance as the Classic III SL which is in the Slim-Line housing, like the XLT was introduced in.
The Classic I and Classic II used the older type coils, and with the Classic I it was a fixed (hard-wired) 8" and an interchangeable 8" on the Classic II.
The Classic III SL, then Classic ID had the interchangeable Blue Max series coils, like your unit uses, so they could have one of the 6