$2.80 is the rate for 8 ounces for a first Class Parcel.

This chart might help:

Here is the post office rules on physical standards. Have fun:
http://pe.usps.com/text/dmm300/101.htm#wp1039555+

Robert
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Buck Jones in "Stone of Silver Creek" (1935).
http://www.antiquegamblingchips.com/StillsD_Westerns.htm