This topic comes up from time to time. For about 20 years, I kept an on-again, off-again journal of mandolin serial numbers from instruments I'd seen in person, or seen ads for on the Internet or magazines. When Dan started the Archive, I was one of several who contributed such lists.
That's one of them. All I can say for sure is that we never had that instrument for sale at Gryphon, so its number came from another source.