Thread: Is registration number of any relevance to A-cat rifles?

I watched some youtube vid how to paint a rifle and the guy pointed out to put a tape over the registration number so you don't paint over it. That was a very useful tip because I didn't even consider that my rifle had a registration number (the number is so small I could barely see it until I looked carefully for it).

That got me thinking out of curiosity, do registration numbers have any relevance to A-cat rifles at all? Is it illegal to have a rifle without a readible registration number or would that be completely irrelevant for an A-cat anyway?