cudamark, tsk tsk, you say:
".
.......without using any negative buzz words (like digging, cutting, historical artifacts, etc......"
Huh, why? Wouldn't you want them to understand the full impact of your question? What if (gasp) that teller or bank person happened to be passing by in the ensuing week, and SEE you out their "digging" and "cutting"? Or is she/he viewed ebay in the ensuing weeks, and saw a rare barber dime she surmised you found on the bank's property?
Hence, ... no. Don't mince words. Be totally forthcoming. Let them know you'll "dig" (yet be careful of utilities, be careful to cover back up, etc...). Let them know you'll potentially find gold bars (afterall, it certainly *is* possible). Let them know you'll alert an archie if you find an indian bone (they'll appreciate your integrity on this point as well). And in addition to all that, be sure to put a contract in front of them for them to sign, authorizing you to "dig for treasure" on their property.
Now ......... go do the right thing. Afterall, you "wouldn't want to get arrested", now would you?