The first three characters usually form the builder id. The rest of the numbers identify the hull.
In North America, these first 3 characters may be:
PFS = Performance Sailcraft (1971-1974) (Montreal, Québec, Canada: still manufacturing outside of the Americas.)
ZFS = Performance Sailcraft (1974 [as per hulls 16950-51626]-1985) (Point Claire, Québec)
PSC = Performance Sailcraft (19??-19??)
PSL = Performance Sailcraft USA (Owner Don Trask, San Rafael CA, 1973 to early '80s?)
PSI = Performace Sailcraft International (South Africa, until 1989)
ZID = Laser International (Ontario 1984-1991) Reincarnation of original Laser builder. (Also known as Performance Sailcraft Canada.)
PSB = Pearson Small Boats (1989-1991) (RI)
SLI = Sunfish Laser Inc (1991 to March 1997) New manufacturing facility.
OQT = Vanguard Sailboats Inc., RI (March 1997 to present) Initials stand for Quarter Moon Inc. Production continued in SLI facility which Vanguard purchased.
Next 5 digits are the Sail Number. If the sail number is great than 99,999, then the first digit is a character, where A=10, B=11, C=12 etc. (i.e. a letter followed by 5 digits).
Last 4 characters indicate when the boat was built and the model year. Usually 1 letter followed by 3 numbers. The letter indicates the month of manufacture (according to Sunfish/Laser Inc.): A=Aug, B=Sept, C=Oct, D=Nov, E=Dec, F=Jan, G=Feb, H=Mar, I=April, J=May, K=June, L=July.
The next number indicates the year the boat was built (not model year!), followed by a 2 number model year. Eg.
D494 = Built Nov (D) 1994 (4) for 1994 model year (94).
F697 = Built Jan (F) 1996 for 1997 model year (97)
For example: SLI F1234 F494 = Sunfish Laser Inc, Sail number 151234, Built in January 1994 for Model Year 1994.
Older lasers: Last four digits of sail number may be missing or belong to an unknown code (e.g. ZFS 33426 0376 = march '76?). Boat manufacturing codes seem to conform to some industry norm - an Alden Ocean (rowing) shell hull number has a similar format.
1971 to 1973 Hulls: Sail number is only found on deck, under the bow eye. It is also reported that following the Laser prototypes, the first mass-manufactured Laser was numbered 101.