MDI glassine pack

MDI glassine packs were products of Minnesota Diversified Industries made for the USPS. They first appeared in the mid-1990s and were used through to the early 2000s for use in vending machines.

Like the booklets created by MDI, these packs were handmade from sheet stamps. Not only gummed ("water-activated") and self-adhesive definitives were available this way, but so were commemoratives and international airmail rates stamps. The stamps were folded to fit into small glassine envelopes and sealed with an identifying sticker. Packs with only a few stamps included a slab of cardboard to allow proper dispensing of packages from vending machines.

These have been largely ignored by collectors and catalogs.  File:US MDI glassine.jpg 

See

 * MDI booklet

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