Date-coded serial numbers are typically found stamped on the back or top of the headstock, and "Made in USA" is stamped next to the number starting in June 1967. The next digit = last digit of the year (1966 to 1972: 6,7,8,9,0,1,2).
The remaining digits = number of individual instrument, probably.
In 1949 they switched to round badges in solid metal colors.
Slingerland is a drum manufacturer originally based out of Chicago, Ill., that has produced quality drum sets and snare drums since 1928.
The drum brand was famously played by Buddy Rich, who's still considered one of the greatest drummers of all time.
Date your Slingerland drum by identifying the veneer of the drum.
The veneer is the exterior covering used to protect and color the drum.
From 1961-86 they were manufactured in Niles, Ill., and for one year from 1965-66 they manufactured their drums in a plant in Shelby, Tenn. Copies of original Slingerland ads that show the drums in their original condition and note the dates they were sold can easily be found and purchased online.