A lot of manufacterers have an "1164" wrench - in size 5'8". How would a 5/8" nut or bolt look when inserted in the wrench? Photo?
I tried searching for CMP, CMR, MPC, MRC with no solid results. There is a vague similarity to a firearm barrel wrench but I don't think that's a good match because you have that 1164 designation.
Al