Production Codes
Most Plantinga products have had a production code on their caps, at least since 1991 but probably already at least 10 years earlier.
During UTO times (until 2004) the code could be deciphered as follows:
PDDDYQQ
P = Production line nummer
DDD = Xth day of the year
Y = Last digit of the year (which unfortunately allows for easy confusion between 198x, 199x and 200x)
QQ = Xth quarter of the day
When production went to Boomsma, the code consisted of two lines and could be deciphered as follows:
LYYBBBB
DDD UU:MM
L = Always an "L", indicating that it's a grocery item
YY = Last two digits of the year
BBBB = Batch number
DDD = Xth day of the year
HH:MM = Production time in hours and minutes