Hi Gregg,
I’m sure you know that the engineer of the MDT8000 is the same fellow who used to work at Fisher Research Labs back when they were operating out of Los Banos in California, prior to their purchase by First Texas Products.
His name escapes me at the moment. He was the designer of the Fisher Coin$trike and Gold$trike detectors, as well as (I believe), the ID Edge and Excel detectors.
NASA Tom Dankowski is his collaborator in testing and promotion and there is a 68 page (& growing), thread on his forum all about this machine specifically.
I was following some of that thread at its inception and my take is that the design brief was to build a niche detector targeted specifically to the needs of serious beach jewelry hunters seeking gold drops on mineralized beaches and in the surf. Relic hunting was not what it was designed to accomplish, and different coils are apparently difficult to produce for the multi-domain operating concept. I think it was meant to give more ID depth on the salt beach vs multi-frequency VLF units, probably hoping to compete with PI units by offering visual target ID and discrimination.
Hope this helps,
Cheers,
Drew