Belgian Congo from Belgium 1921 Postage Dues

Incoming mail envelope bearing Yvert 140, 20c lilac tied by Liege Dover-Ostend slogan, underpaid with TAX handstamp addressed to Leopoldville with Belgian Congo "15c on 50c" black & olive overprinted TAXES applied to the cover as postage due in Leopoldville. Scarce item of Postage Due mail. (pt)    ID: 14063