Can any of you help with these questions and/or supply references:

(1)When were plastic caps (tops) introduced for bottles in the
        20th century?

(2) When did such caps become common - so it is likely they would
        be encountered in the archaeological record?


                                                Thanks,

                                                        Bob Schuyler
Robert L. Schuyler
University of Pennsylvania Museum
33rd & Spruce Streets
Philadelphia, PA l9l04-6324

Tel: (215) 898-6965
Fax: (215) 898-0657
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