1945 narrow gauge, SP means specail parts, higher gears in trans, cab ,gen and lights or anything else that was not standand assblyline parts. It was built during wartime and as every track type machine made during war by any company it was OD Green but not all were milt. some were alocated to farmers and contractors, if it was milt it will have heavy cast id and instruction plats bolted to it in diff places