10 kopek charity stamp of 1915 overprinted and surcharged "СССР уполно-мочен-ный ЗАГРАНИЧНЫЙ ОБМЕН. по фи-лателии и бонам. 75 КОП. 75" in black
This is a revenue stamp which was used to pay a tax on stamp exchanges carried out through the Soviet Philatelic Association. It was affixed to incoming or outgoing envelopes containing stamps and it would receive a violet or black rectangular cancel.
Listed under "Gebühren für Briefmarken-Tauschsendungen" (Fees for postage stamp exchanges) in Michel, "Timbres d'Usage Spécial" (special usage stamps) in Yvert and "Exchange Control" in Barefoot.
