Zanzibar 1876 India 12a Venetian red, with very fine large part type Z5 squared circle (three bars at corners) dated 'NO 3' (apparently without year).
A fine quality example of this very scarce postal cancellation.
The Stanley Gibbons catalogue value is £100.
Stamps of India were used in Zanzibar from 1 October 1874 until 10 November 1895, when the administration of the postal service was transferred from India to British East Africa.