I found that "mules" can be fairly common in US currency. The same back plates were used often during the switch from the $1 notes of the 1957B series front plates to the 1963 series front plates. And that was the series switch from Silver Certificates to Federal Reserve Notes! In fact I sometimes find it harder to get the 1963 series $1 notes with new back plates. Do the "mules" have a premium even if only minor?
I find "mules" in general are like anything perishable as in the beginning, when discovered everyone has a high interest in them.. take the 2008 rev of 07 ASE... when first discovered man the demand as well premium was hot...after a while as well 47,000 being known to exist...they fell in price as well favor. I had several 70 's no one was willing to pay 70 money...when a 69 was less than half of the 70 money. As a variety collector I can assure you everyone likes and wants them...but paying a premium on them...their interest falls off. Now correct there's alway one buyer out there...ask yourself whats the odds that you will meet or find them?
The only modern mules that I know of that demand a minor premium are the series 1963 $1 B-B and G-B mules.
