That is a Murray/Sears serial number. Definitely a Murray made frame. The cantilever bars go into the frame instead of beside the frame at the front says it is a 65 or earlier. If the front chain wheel is original to the bike means its considered a juvenile bike originally. Would not have had a banana or polo seat. Would have been a saddle type seat or possibly the very small non sissybar type polo.The numbers look like
477936
502683