Your serial number is actually not that low, as being one who had done a lot of research on SAC guns, I'd need to see a number below 100 to get very excited. As to value, I never assign hard values to another's gun; but the Grade 2 and Grade O SAC Hollenbeck/Syracuse guns were the company's sales leaders and are the most common models found today. So unless your gun has some special feature/s, or remains in near new condition finish wise; $200-400 is about the market (and less, if the gun is damaged, has pitted barrels, or has been unprofessionally repaired/restored). You can get an idea what is being asked for such similar guns by checking the on-lin Gun Broker auction and watching those auctions.