You might check The Great Britain Philatelic Society's page linking to directories of post office numbers from 1844. Link is here: http://www.gbps.org.uk/information/po-numbers/
Per the date stamp on the cover (lovely by the way), A93 was allocated to Llanfarian, Cardiganshire, Wales.
Thank you good people now I just need to find the name of the Cunard Line ship it sailed on Rich
Hi Rich, This is a very nice-looking mourning cover. However, I doubt it was ever carried on a Cunard ship. It would have travelled from Wales to London, across Europe by train to Brindisi and then by steamers through the Suez Canal and on to India. Is this just a front or, if you have the complete cover, are there any transit or arrival marks on the back?
Hi Nigel It is a complete cover no contents. Rich
Thanks Rich. That looks like a "SEA POST OFFICE" cancellation from the Indian Post Office. This would be applied when the envelope was being sorted on board a P & O ship between Aden and Bombay.
Here's a useful link on this service from the website of the TPO and Seapost Society: http://www.tpo-seapost.org.uk/tpo2/spadenbombay.html