Just called him. Turns out it's in a plastic barrel, not a steel one (and I really wanted to use the barrel as a burn barrel in a specific location so I can burn in place rather than drive tractor or backhoe across yard pulling fallen trees down.... oh well)
So it's a plastic barrel. He thinks it's about 55 gallon in size ("full size" he said) BUT it's only got 20-30 gallons in it so they must have drawn it down when they worked their land with the bulldozer.
He said come & get it and it's mine so after this incessant rain stops I'll drive the backhoe down there and figure out how to carry it back.
He also said it had a bung on it rather than the lid being removable. That's got me hoping that it's not had as much condensation in there. Never having had to deal with old diesel (he verified it's TEN years old)....anyway, having never had to deal with old stuff I was wondering if algea might have taken hold in there by now and what issues that might present, if any.
This said.... if it is an intact, good condition barrel, NOW I'm wondering about using it up.... cleaning it out and then putting it on one of the small trailers to drive to the Co-op and use it to carry diesel from there to here. That might beat having to lug 6-7 five gallon jugs every several weeks..... crammed in the trunk of my Camry!