Engraved French and French colony stamps issued during the 1950s through 1970s are subject to toning from acid in the gum used.
What type of authentication or certification do they offer and from whom ? There are thousands of "varieties" listed in many venues that are of only curio value.
re: Congo stamps : color Variety or light alteration
Engraved French and French colony stamps issued during the 1950s through 1970s are subject to toning from acid in the gum used.
re: Congo stamps : color Variety or light alteration
What type of authentication or certification do they offer and from whom ? There are thousands of "varieties" listed in many venues that are of only curio value.