'
One wonders if the Iranian Post Office had an issue, post-1979, with domestic mail franked with stamps bearing the image of The Shah.
Ditto the Bolsheviks post-1917, The Communist Party of Cuba post-1959, the Communist Party of Vietnam post-1975, et al.
Q/ Did they issue new stamps, and then allow citizens to turn-in their old stamps for new?
Even if rejected or postage due covers are rare to the point of vanishing, there might be copies of public notices.
Q/ Did USPoD publish a notice when US stamps were demonetized in 1861?
https://upload.wikimedia.org/wikipe...tisation.jpg ... New Zealand Post Office demonetization notice of 1935
Cheers,
/s/ ikeyPikey