Savage elected to serial number most of their guns prior to the GCA making it mandatory. However, many of the more budget oriented utility models (219/220's, 94's, etc.) frequently weren't and/or had periods where they were and weren't serial numbered. I think the latter likely has to do with the various different owners Savage had during that time frame. As with most anything Savage, getting accurate and reliable historical data is darn near impossible - again primarily due to the multitude of owners and poor record archiving from owner to owner.