New Surplus, Acquired From Spare Parts Storeroom.
Length is an estimation. I weighed out 1 pound of cord and measured the length at 555 inches. I weighed the whole coil at 10.5 pounds. I estimated the weight of packaging at 1 pound, which left 9.5 pounds of rubber cord. 9.5*555/12 ~= 440. I'm giving myself some margin for error, so I'll call it 400'.