Spent my Air Force career in satellite communications. the challenge coin spare tire is from the 4th Combat Comm Group (Guam). I made it using; fiberglass, foam, steel and plywood. The 50 caliber M2A1 was demilitarized by the army - it is non functional - no one knows it, so I'm never cut off in traffic. I'm more of a woodworker than machinist so I build everything out of wood, fit it on to the jeep, take it off and hand it to my neighbor, who has a full machine shop - he hands it back to me in metal w/ in 1/10,000" of what I hand him in wood.