Thanks! Honestly, I never even thought about potentially being a deformed keg. But that certainly seems the most likely answer. Especially since all the stamped lettering makes it seem that it should have a standard lid.
That lid you're linking to is the standard corny lid. Not sure why it shows as racetrack in your search and not sure why the picture makes it appear round-ish. That's the same lid size as pictured on my keg.
I don't recall seeing anything stamped. I will look when I get back home (I hope)...
A while back I picked up some ball-lock kegs from a guy getting out of homebrewing. He had one keg that was different. Still ball-lock fittings, but has a different sized hole for the lid. He couldn't find the lid that went with it, but gave me the keg anyway. The hole is more round than...
Not an active member of the board at all, but I thought I would add...
43 oz. Hallertauer (probably Mittelfrueh).
568.645 + 43 = 611.645
Hope to have another bunch harvested this weekend too.