is that the enhanced mode is designed for pre-1950 sites that HAVEN'T BEEN USED SINCE THEN. If any site has seen use since 1950, when in the enhanced mode, the aluminum trash is going to cause the 3D to signal a good coin target when in fact, it's can-slaw or a tab. That's why they recommend using the salt mode at more modern sites.
I've started doing a lot of research for my area this winter, and have realized that while some areas had activity, then were abandoned, many sites have seen activity for over 150 years at the same site. So, if I had a 3D, use it in SALT mode in the trashy areas.
I live in southern MI, and because of all the small iron in the dirt, I normally hunt in SALT on my CZ-5 anyway.
HH from Allen in MI