USPS Glassine Envelopes

I know some people collect glassine envelopes with advertising on them, so I thought I'd post this one I just uncovered from the USPS circa 1980's, I imagine when Express Mail was first introduced:



I would think that using 2-color printing on these envelopes would have been expensive. With the current USPS financial troubles, I wouldn't expect to see that kind of printing again anytime soon. In fact, with all stamps going to PSA's, I suspect they may discontinue offering these glassine envelopes altogether as they serve little purpose with the self adhesive stamps.

Thank you for this. That's quite marvelous.

I still get the plain old glassines at the post office every time I go but not a fancy as these.