Take a #2 pencil and go back and forth over the #s and overlapping each end. Next take a strip of scotch tape and place it sticky side on the #s. Rub your finger over the tape back and forth while pressing the tape ,#s will transfer onto the tape. It may take several tries to get a tape lift that you can read. Place the tape sticky side onto a sheet of white paper and you can with a little luck read the #s and if you use a magnifying glass it will also help. That said if your #s are all at r/angles and inline it may be as Royse said,an all the factory #s were done at all angles and spaces varied . However I have seen some with no #s at all just blank and was told it was a replacement block. I would think yours could be that and someone just put there own #s but just a guess.