I may have seen a pattern in some GT Dyno Kustom Kruiser serial numbers, although from a limited sample, from cruisers of family and friends. Perhaps what might be more interesting would be production numbers and statistics (probably proprietary, trade secret information). For example, when was the peak in production/sales, and how many cruisers did they produce that month and year, (or any/typical M/Yr), and what about those less-interesting models. So from a limited eight (8) frames, six (6) start out with "MT". I'd like to think that stands for "Made in Taiwan" but have read of other prefixes like "MB" (chopped?).
After the MT, was always a "9" or a "0" and (as other have suggested) this may mean the Year, and that four (4) were 1999's and two (2) were 2000's. After the 0 or 9, was always a "0" or a "1" and on a 3/1 ratio. This leads me to believe that this digit and the next, together form a Month code. One of the bikes had a MT903vwxyz serial and the handlebar was also stamped 99.03 under the left grip; i.e., March 1999, a match!
After those three digits were five more numbers, which all started with "0" and seemed to increase with the month code. I take that number to be a 5-digit sequence number that (with others) reflects upon the number of bicycles produced in a month/year (less than 100,000). It is hard to tell, since one does not know if a bike is the first or last produced in a month. The few numbers reflect about 700-1000 per month and rising in 1999 and a relative slowdown to 200-400 per month in 2000.
I also once saw a badge-less stamped F97- on top and 1xyz on the bottom bracket, perhaps from Fall 1997. Also, a "KK" version marked SNMT104uvwxyz (perhaps from April 2001) with an additional 6th digit for the sequence number, yet reflecting a further decline in only 150-200 produced per month.
What might not make sense is that those frames were for both Men's and Women's model's and the 1999 SN's did not distinguish between those, or Glide-Seven version, or new versus old Kickstand styles.
Some production lines may not use a first-in first-out (fifo) inventory management, or may even "skip" serial numbers (cancelled orders). I recall a couple of bikes advertised as "1980's" GT Dyno's, but expect that rather the Seller did not remember - or by mistake, simply Google'd the manufacturer of some 1980's BMX products.
