Multiple Franking To Send A Cover

I'm interested in seeing covers that used more than one country's stamps to send a letter.
Here is one that I have:



Chad Scott #81 and Congo Scott #91 (pair) postmarked June 24, 1962 at Bangui Airport in Central African Republic. Several years earlier, all three countries were part of French Equatorial Africa.

The CFA or 'Communauté financière africaine' is still in use today.
This has provided monetary stability in numerous countries.The CFA was pegged to the French Franc and now the Euro.It is a currency guaranteed by the Bank of France.There is an on going discussion of adopting the 'ECO' currency by some of these countries to break away from the CFA....

I found this one in a trash can at work many years ago. The proper postage at the time was 29 cents US, but the sender used a Great Britain Machin and a 15 cent flag stamp to illegally send in his insurance payment. (I intentionally blurred out the return address for privacy)

Linus

One I had posted before, German and Brazilian stamps on same cover.

Would the 26 pence stamp on Linus' cover have an exchange rate around 21 cents at the time which would be more than enough to cover the 29 cent rate when combined with the 15 cent stamp?

The Great Britain stamp has zero value when used in the U.S. The cover is underpaid and was not detected, which is extremely easy to do with modern facing/canceling/sorting technology. With today's mechanization, a typical letter dropped in a blue curbside box will never be seen by a human until the placed in the destination mailbox.

I see two broad categories to this thread:
1. legitimate needs for the stamps of two countries in order to transmit the mail piece. (It really paid the rate.)
2. squirrelly/philatelic uses which may or may not get caught. (One country's stamps counted for nothing.)

https://goscf.com/t/78169

I posted a similar thread before I found this one. You may want to look at it.

Thanks WillUK! Your thread is what reminded me about the cover I posted.