I think you may have omitted one of your original pictures as the first and last ones above are identical.
The "J?A" mark I read as JEA. It seems pretty much identical to a maker's mark registered in London by James Ebenezer Allcock who was in business as a gold and silver mounter and is listed in a trades directory as a stick maker. This version of his mark was only in use from 28 Jan 1888 to 26 Nov 1888 after which he used JA. However I can't convince myself that the mark above that is a London hallmark:
although the central component could be the uncrowned leopard's head.