Hello Kevin -

I have found this discussion so I can show some of my pre-1/1/72 to German States. I'll start with some lower denominations.

This is a grenzrayon letter, 20 centimes, went a very long way for the rate.
The routing can be followed:
Altstätten 23 Mai 1866 to Freiburg im Breisgau, Baden.
Chur-St.Gallen[23 Mai]
St. Gallen-Olten [24 Mai]
Waldshut DE: Basel-Constanz Bahnpost [24 Mai]
(Schweiz uber Baden in oval),
Freiburg-Basel [24 Mai]