7.62mm barrel question, possible L8?

[Roger Payne]

I was sent two near new barrels from a friend in Canada a few years ago. They possess lugs & appear to have a radial recess machined into the back face (breeching up face). There are few markings other than a rather odd shape that looks like an asymmetrical star together with a three digit number starting with a six, in both cases. Can't remember the exact numbers but something like 639 & 642. Does this ring any bells with anyone? I hope they're Canadian as I have plans for them if they are....

ATB