RPO Cancellation Stamp

I have an envelope from my late grandfather with an RPO cancellation stamp on it. Somehow, he knew of a special RPO operation on a tourist railroad, I forget which (the envelope is in my classroom, stored away safely), and using the mail drop on the RPO, mailed it to himself so he could have the RPO cancellation.

I wonder if the U.S. Post Office today would be willing to allow the C&TS to run such a special on occasion. I can envision post cards being cancelled and sold as a small revenue generator. The RPO could be pulled in a regular service train for the cancellations to take place if that would reduce the overhead associated.

Or, the cancellations could be done on a special train pulled by the 168.

I think it would be cool. The last RPO was pulled from service in 1968.