I wrote to the London assay office, and they were very helpful and wrote back immediately that PPM is the mark of Presman Precious Metals, who first registered with them in 1977, and were registered until 2003. .
Hi Mike, Thank you, that is very helpful. The first mark is definitely not the post-1904 import mark for London as given here . I would be looking for a London import mark I guess? Or could a different country stamp their import mark next to London marks, without adding their own marks for the rest ...
Thanks to this wonderful website I'm checking out the marks on my jewelry, and having loads of fun - thank you all for this great resource! I'm hoping for some input on this ring (clickable thumbnail): http://i208.photobucket.com/albums/bb198/irisalsusername/ring/th_ring.jpg I always assumed this wa...