Well, it's definitely an import mark but your picture is too unclear to see the finer details. I assume it's London as it is with a London mark that I have seen this (unknown to me) AJ sponsor's mark and that the date letter is from the 1916-1935 cycle. It may be "n" for 1928 or "u" for 1935 - or perhaps something else?
Many thanks for that. It is pretty tricky to see and pretty tricky to photograph as well. I'll see if I can get a better image of the marks and I appreciate your reply.