Pierre Courtiade wrote:

The country is Central Africa.
The FDC date is 16 may 1966 on Scott # 72 ; a second cancellation was
made on 26 july 1966 at Bangui airport.

That seems a bit long for a "grace period" (nowadays usually 1 to
8 weeks depending on the country, at least for pictorial cancellations).
Maybe this is why the second cancellation has been applied.

Jan-Martin