I get the feeling you are trying to say that a 520 doesn't exist. And, frankly, you're wrong. I had a Bacchetta Corsa 24" that used that size (by ISO measurements) for both wheels. Also, Terry bikes of earlier vintage that had 24" front wheels used the 520 size. The Terry website still sells the 520 tire, but it is a bit thinner than what I want.
My post was NOT to question the ISO of my wheel...my post is asking if anyone knows a source for a tire that will fit that rim size.
I don't know what your objective is, other than insisting on being RIGHT (you're not)...but. just. go. away...Thanks but no thanks for your "help".