First off, just curious: why do you think your item(s) will, by necessity, be "9 ft. deep"? There is often the misconseption that "the bigger/better the treasure, the deeper it must be" or something like that. You've got to remember, the person who stashed it for safekeeping, would no doubt have intended to some day retrieve it. So if the goal was to hide it from anyone else knowing where it was, what difference is it from 3 ft. to 9 ft? The surface of the ground remains looking identical. If you've ever dug a hole, by hand-labor, 9 ft. deep, you know you're talking hours, if not all day just to reach that level
Or is there some sort of aluvial sediments or historical soil deposits that lead you to believe they're now this deep? Because if not, then don't think that old-timers necessarily stashed their stuff, on their own accord, that deep. Heck, sometimes they just stashed it in the walls of their homes or whatever.
To answer your other question: The TM808 is made only for larger objects. It will not work for anything smaller than a soda can. For a soda can, it'll go several feet deep. For a coffee-can sized object, perhaps 5 or 6 ft. deep. For a Volkswagon, perhaps 10 or 15 ft. deep? These are just depth guesses off the top of my head. Someone else may have better stat's in that dept. So it would depend on how big of a stash of silver coins you're talking about. If you're talking just a handful in a little leather pouch, then no. It won't reach 9 ft. for those. If you're talking about silver coins in a big wash-basin sized container, then yes, it would reach them. If you're talking a coffee-can sized container, that's a good question
