Even older civil war cannon balls are still a valid uxo threat here in the conus .
....Many render safes when stationed in Europe with WW I and II era ordnance found during surface and subsurface clearances or by civilian construction crews and farmers. Then there is crap the resistance and other underground groups cached that pops up still to this day by mother nature or human nature.
Business is boomin still..... Nite !
When I was in Germany during my first enlisted tour there, I was priviliged to assist some old veerans with the removal of certain explosive ordnance from one of those exact same WWII caches, underground about halfway between Munich and Augsburg, not too far from the former Messerschmitt A.G. aircraft factory. The cache included several dozen MP44 and MP40 SMGs and ten or twelve wartime P-38 pistols, not a P.08 *Luger* in the bunch. The ammo for them was tested and found to be okay, and left right where it was. The old Panzerfausts, however, were disposed of. And, I suspect, were replaced with newer ones.
I'm sure they had all sorts of other novelties in other location.
A decade or so back when the Finns were trying to inventory and rationalize some of the military material that's accumulated their during their last three wars, they came up with all sorts of ordnance, including one Finn farmer with an 88mm Flak 18 in his barn, which he towed in behind his tractor, along with a couple hundred high explosive and antitank rounds for it.