South Vietnam, Nam Phương with Red Cross Overprint, November 10th, 1952, Michel Nr. SVN 88; In order to generate donations for the Red Cross the Nam Phương stamp was overprinted with the number +50 and a red cross. Vietnam was still very poor so the stamp was not very popular with the general population and it was mostly used on philatelic First Day Covers and mailings.
Here is the mint stamp
The stamp was not officially released imperforate, however a small number of imperforate trial proofs have come to market. Here is one of them
Beware of overprint forgeries. Sometimes double overprints are offered that show indeed two overprints but the vertical distance between the red cross and the +50 differs between the two overprints. This, of course, is impossible as the overprint was executed in one step and hence the distance between the red cross and the +50 would have to be the same.
Postally used stamp
There was also a stamp booklet that was produced with these stamps by Helio-Vaugirad in Paris. It contained twenty of the overprinted stamps in two horizontal rows of ten. The stamps were protected from adhering to the booklet carton by parchment paper placed above and below the stamps.
Mixed franking of one of the overprinted Nam Phương stamps together with the 1.50P Bảo Đại Birthday stamp paying an overall postage of 3P on a local letter sent within Saigon. Special red Re Cross cachet on front. Special First Day of Issuance cachet on front.
Mixed franking of two of the overprinted Nam Phương stamps together with two 1.50P Bảo Đại Birthday stamp paying an overall postage of 6P on a local letter sent from Saigon to Cholon. Special First Day of Issue cachet on front.
Registration Nr. 200060