Help Needed: 2c Overprint?

This peculiar little thing has been sent in to me by a reader, with what appears to be a “c” overprinting the value “d,” changing it from pence to cents! Unfortunately the cancel is too indistinguishable for me, but if anyone out there can help, then please contact me. The logical conclusion would be that it was a private overprint, since nothing has been discovered about it in the extensive records of De La Rue, however if it turns out to have been sent from a British territory and not from the UK, then it is a very interesting item indeed!