Hey Dave, I have my doubts if serial numbers are required by law on guitars. I think, from what I've read, that serial number marking on guitars began back when "build order numbers" began to be used in manufacturing to track an order through the factory. The purpose being to make sure all of the components come together for a specific customers order and then shipped on time. Therefore the original purpose is more linked to productivity, customer service, etc., not so much to give a guitar it's unique ID. I've read that even for Gibson they did not get a handle on serializing guitars well until the 1970's.
For Mosrite, it would make sense to me that during it's hayday when they had ~100 employees that the condition would also exist to track orders through the factory for such business purposes as well. Coming from a Quality Assurance background I can certainly recognize how easy it would be for guitars to get out the door with duplicative serial numbers or no number at all. When you take into the equation that there were at least two fires that I know of which probably destroyed any documentation; as well as during tough business times when there were few employees or no employees at all; and consider turnover, training new people, people make mistakes, and the list of variation possibilities goes on and on, it's going to be tough to nail anything with certainty.
In my opinion, the best we can do at this time is to recreate the information by having a master list, or registry, or some other manner to document and record the guitars that are still in existence today. Due to my passion for the Celebrity models, I intend to do exactly that with my research and website. Perhaps someone else will pick up the torch for the other models (hint, hint!). Time will tell!
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