Some of these crown cap answers seem to conflict with my childhood memories.
When in elementary school (approximately 1958), kids used to collect bottle
caps to flick in the air (snapped fingers sent the cap flying like a Frisbee
today). The top flickers sent the caps the furthest or closest to lines drawn
in the sand. I recall experimenting by putting pennies in wax to lend weight
to the flick. Those caps at that time were cork. At that time, my family
engaged in hotelier work and the bottle caps with foil were mixers and tonics
from the bar. Maybe I was just observing the transition point in technology. In
truth, I don't think I ever gave bottle caps much thought after 1959. This
would place west coast bottle caps with cork liners a tad later than the 1955
rule.
Ron May
Legacy 106, Inc.