The Royal Bank of SCOTLAND £1 Banknotes of All Nations

Description

While this is both a notaphily and philately item, I suspect the greater interest may be in the £1 note so I have listed it accordingly. I have no idea who produced this series, but as you can see, it is a philatelic cover of sorts franked with a S31 10 1/2p regional stamp and cancelled on March 23, 1981.  There is a plastic window both front and back of the cover to protect the note, which appears to be in pristine condition.
The cover measures 11 5/16 by 6 inches.