Tresor et Postes 222 Indo China

[Peter Harvey]

I would be grateful if any member could assist with this cover.

Oct 1949 French cover. In red under the stamp I assume a Unit cachet authorising free mail, returned to France from India China and the usual POSTES AUX ARMEES T.O.E applied (Theatre d'Operations Exterieurs), franked 25F for onwards travel to Austria and the stamp cancelled TRESOR et POSTES 222 (in France).

I am however interested in the red 'D' cachet and the significance of this?

Any thoughts please