No way to restore the number but if you remove the paint chemically so as not to reduce it even more you may have some luck. I have taken white rubbing compound and smeared it across the number and at times it has given enough contrast to make out the number. Looks like a Schwinn the first two characters should be enough to date the frame. The numbers moved to the drop out in 1950 I believe so that helps a bit. How about a pic of the whole bike.