The first polyester fibers were produced by reacting ethylene glycol and either terephthalic acid or one of its esters to give poly(ethylene terephthalate). This polymer is still used to make thin films (Mylar) and textile fibers (Dacron and Fortrel).
This stamp also may be used for mailing items weighing up to 2-ounces. These Forever stamps will always be equal in value to the applicable price for the price category printed on them, at the time of use. The initial price and value for this stamp is 71 cents, effective May 31.
â¢Used US postage stamps printed in the last 70 years are worth almost nothing. â¢ Mint with original gum US postage stamps printed in the last 70 years are, with a few exceptions, worth less than their face value and can be used for postage without worry. I use old stamps back into the 1930s as postage to mail envelopes.