John Argo or John Allen?

Dear Silver geeks,

I’m trying to find a book or information that will clear up the confusion between the scottish provincial silversmiths John Argo and John Allen hallmarks. There seems to be a myriad of mixed opinions on the hallmarks; “JA” “J.A” “IA” and “I.A”

If the mark is accompanied by the Banff townmark, then i know there is a good chance it is John Argo, and if there is a Paisley or Aberdeen townmark then it should be John Allen, but is this absolutely definite?

If the item does not contain a town stamp or it is too worn to distinguish, is there any information out there that might help me to identify the maker?

Any help you could give me would be greatly appreciated!

Nick