I was told it is a 8mm. He said outside of that he didn't know. The rear site is missing the adjustment blade. It looks good over all. My questions are as follows.(1) Is it a 8mm? (2) How can I tell what country its from? (3) How can I check the head space? (4) What ever else you can tell me about it? If you need any more info please let me know. I bought it for $82 out the door from a local dealer. Thanks Hobby101