Quote:
I have seen more than one envelope that was turned inside out and used again
That was quite popular in the Gilbert and Ellice islands, I have some. It is STILL being done by the Tuvalu Philatelic Bureau to some extent, due to shortages of packing materials. Mostly it is left-over unused first day cover envelopes turned inside out and taped back together.
Believe it or not, there IS a philatelic term called
Turned Covers.