The Hungarian 1919 "Issues of the Kingdom" is overprinted as above to commemorate the Romanian withdrawal. According to Scott, the overprint reads "Entry of the National Army-November 16, 1919".
There is a note to indicate forged overprints exist.
But turning over the stamps, all of them -save one- (Scott 306-310) have this printing on the back in different colors. Only the 5f green in my collection has no printing on the back.
Marque Garantie SOC MIS
Scott makes no mention of this.
Was this to guarantee their genuineness?
Are these "official" markings?
Or are they private?
And,is this a mark of a genuine - or forged overprint stamp?