Im thinking this might not be UK based ? Any ideas?
You are correct. The mark is the import mark for London and the date letter ‘r’ is 1912/13. The 925 indicates 92.5% silver, the fineness of sterling. Can’t help with the sponsor’s mark though. Some sponsors dealt almost exclusively with imported wares and watch cases are a fairly specialised item.
Hope this helps.
Thank you very much Tony for your prompt reply.