India 1865 QV 1a Brown Used with Small Circular Numeral 4 cancel?

Queen Victoria watermark Elephant Head 1a brown used. With small circular cancel which looks to be 14th April 1868 cancel with 4 / ?LTO at top - I am unsure what this cancel is and whether it is postal and additional ink cancellation. With one missing base perf.

Year : 1865

Reign : Queen Victoria

Catalogue No : SG 59

Condition : Used

Price : highest bid