Details
used --66 (Oct) 8a. purple overprinted on complete stamp inscribed "FOREIGN BILL", a remarkable example neatly cancelled with c.d.s.; a few trivial faults though believed to be unique and certainly one of the great rarities of Indian philately. Ex Koh-i-Nor. R.P.S.Certificate (1935). S.G.O18, #6500. Photo
Further details
Note: The above example is illustrated on page 122 of "Stamps of India" by Jal Cooper.