here's one

[krusty the clown]

i have no clue what this is but i hope you guy's do.......
5/8 male and 7/8 female square, 7/16 hole bored though it. the only mark is a 7. it was in a toolbox i bought but it may not be a tool?

[john k]

Looks like a socket made for dual wheels on old trucks.   The inner dual was held on by a square head bolt on a few brands.  The outer wheel by a large nut. 

[Billman49]

Similar were used on mains water valves - different comanies had different sized keys, and sometimes an adaptor was required to operate a valve with a standard key....

[Bill Houghton]

Can't help, but that's sure a dramatic shot!