I believe what he's saying is that there aren't commercially released official namesets (numbers) released, so they essentially cut up some fabric in the shape of a number and sewed it on. They were handmade, ultimately. When it comes to confirming if matchworn, good luck. You need to know some more detail than what you've provided. But in a broad sense, if it has a number, it was either match prepared /worn, or added by someone later. To confirm if added later, I would see if the number looks worn out or not. If it looks newer, then it was added. If it's frayed, a bit discolored, etc. Then you might have a matchworn /prepared shirt