Your images are not showing. You have the right idea but Google does not seem to be a reliable image host. https://postimages.org (copy the 'Hotlink for forums' code) is recommended. Both sites allow your images to be resized during upload. Remember to use the 'Preview' button before submitting your post.
I hope I don't sound too patronising when I say "well done with the pictures"! Nice and clear and easily identifiable - when you know what you're looking for.
You are right with London, but this "n" is the date letter for the assay year 1908/09. The maker's mark is JW over FCW, the mark of Wakely and Wheeler (James Wakely & Frank Clarke Wheeler). They first registered this mark in 1891 and used it until 1909.