[url=http://ar15.com/forums/topic.html?b=3&f=12&t=172542]Search[/url] is a wonderful tool. [:)] Used "keyhole" in the subject line on the AR boards in the last 6 months.
Cerro Metal products. Yes, I'm sure, I emailed them, they answered.
[url=http://ar15.com/forums/topic.html?b=3&f=12&t=178303]Keyhole forging mark on upper receiver[/url]