Collectible mine ingots.

[Snowtoy]

Any idea of what this may be worth as a collectible?

Found it half buried on my Dad's property, he never worked for a mine, so it was likely left by the former owner(property owned by a grange prior to '78).  All the pics on line are of ounce sized ingots, not the size that I found.

Dimensions, 19"x3.5"x2.5", roughly 50lbs plus, figure it is either lead or zinc, due to the mine it came from in Idaho. 
Other stamps:

Looks like 7% possibly 77%, the "/" of the % looks just like the 7.