I found this on eBay earlier. What is it?
Item description says: “I HAVE REMOVED THE BULLET FROM THE BASE AND FOUND JUST 3 MARKINGS WHAT ARE SET AT 120 DEGREES FROM EACH OTHER. MARKINGS ARE C - 4 - 7”
I have never seen this case type before.
Although he says it is “approx 6 inches tall with base”. So he could well have measured the base to get the measurement of 20mm, and C 4 7 could be L C 4. So it could well be a .50 BMG.