Regarding plastic buttons, I believe it would be foolish to totally disregard
them as a temporal dating tool. The clue is the chemistry of plastic, which
changed radically over the years. With the proper funding and archival
research, we could retain chemists to break down samples of plastic items
dating from bakelite, celluloid, and post World War II chemical breakthroughs
to create a wonderful time sequence for plastic artifacts. I learned this
while working on an assemblage of plastic artifacts recovered from Old Town
San Diego State Historic Park, 1979-1980. Chemists assured me the formulae
for plastic technology changes are distinct, well published, patented, and
sequential. The problem we faced in 1980 was that no funding agency was
willing to finance this research. Perhaps someone else out there has an
interest in pursuing this topic?

Ron May
Legacy 106, Inc.