The coils from the Magnum series (220, 320,420) should all fit the RM7.
There also exists a 12" coil.
The coils from the Yukon series (IB's) seem not to work on the Magnum series (VLF/TR's), not even in the TR mode.
Never found data about coils from other manufacturers that fit Compass.
Anyway, data about Compass'es are hard to find. They even erased on some components the type names (i.e. transistors and IC's). So replacing possible defect components sometimes is a "try and fry" procedure.
After having done a remod of a Yukon 77auto, I am actually working on a Yukon 77pro, battery A-pack gives no juice to test switch, no broken contacts... any idea?
I have a non working 320 that I will throw on eBay in the next 2-3 weeks. I will list it on eBay Germany (the nearest to me), but it will be available worldwide. Make a search every 3-4 days, so you will find it. Keywords will be: metal detector and Compass Magnum.
You can contact me on my mail address, just give the following keywords: Compass Magnum.
Don't specify anything else, at the risk of falling through my spam filter.
HH
Paul