Can someone advise of the exact date/serial number when the receiver was changed from the squared rear corners of the ejection port to the rounded corners? I looked through the A5 bible, and didn't see it mentioned (that's not to imply that bit of information isn't in there, I just didn't see it.) I am pretty well bed-ridden with a flu for a few days, and can't hardly bring myself to open up the safes to compare the ones I have to narrow down the years they would have changed. I have a couple from the 20s, a few from the 30s, two from the late 40s, a handful-each from the 50s, 60, and 70's. It's just one of those things a guy wonders when he is bored, laying here feeling like crap.