Not sure what day the first was built, but it would have a serial number of XXX013, XXX being the day of the year.
I have a redwood neck'd 93. I beleive it's one of the last redwoods, serial starts with 252. So the first day of manufacture would be a few months before Sept 9th.
If I recall correctly, John Page said that the first Flys shipped in June of 93. If you find a Fly wish serial ending in "3RP" and starting in the low-mid 100's (May 1st is 121), it is very early. Back then they were only available in black or white, hardtail, and had white nuts instead of the grey/black graphite nuts.