This isn't at all a detailed comparison, but this sub-forum seems to be right place to put it.  I'm pretty sure these devices are no longer made for any detector models, but it might help someone thinking of buying a used one.  I bought a used FX-1 (for Fisher F75) recently.  I did look for reviews and found a few, but unless I read too fast those didn't tell the key features (particularly minuses).  This is not meant to be an overall review like you'd find in a magazine.  The other reviews you