Some Schwinns came with an unusual 597 mm tire size.

I hope you regrease the thing before you ride it. It is possible for old grease to be dried up in the hubs. Actually, the oil creeps out of the thickener and makes dusty stains around the hubs. At a minimum, carefully oil the hubs and bottom bracket, or learn to disassemble and correctly reassemble bicycle hubs and put in some fresh grease.