Zimbabwe 1980 QEII Unstamped Service Cover Used with Postage Due 10c SG D22

Queen Elizabeth II era unstamped cover sent to Salisbury. With On ?? Service - Mail Free written at top, but this doesn't appear to have been accepted. With 25th July 1980 Hartley postmark, postage due 10c cancelled 30th July 1980 Salisbury and T mark. Reverse with 28th July 1980 Salisbury post office mark.
Year : 1980
Reign : Queen Elizabeth II
Catalogue No : SG D22
Condition : Used
Price : highest bid
Zimbabwe 1980 QEII Unstamped Service Cover Used with Postage Due 10c SG D22Zimbabwe 1980 QEII Unstamped Service Cover Used with Postage Due 10c SG D22