Identifying a Vintage Japanese Pearl Ring with 'Pm' Marking

Question
A dear friend gave me a pearl ring that was in his wife's family for several years. She was Japanese...from the town of Aomori.  It was originally his wife's mother's ring.
It has a large silver-white pearl of about 11 mm....the setting is white and has a marking inside of Pm....big P, little m.  It is a substantial setting and quite ornate.  I am curious what this strange marking means.  And curious if the pearl could be south sea, since it is from Japan.  Thank you very much for your help.

Answer
HI NANCY,

I AM UNAWARE OF THE MEANING OF THE 'Pm' MARKING IN THE RING. IT IS MOST LIKELY AN AKOYA PEARL (A CULTERED PEARL) FROM JAPAN. THE FACT THAT IT IS 11MM DOES NOT MAKE IT A SOUTH SEA PEARL. MOST SOUTHE SEA PEARLS ARE LARGER AND NOT SIVER WHITE IN COLOR. MOST PEARLS SOLD IN JAPAN ARE JAPANESE UNLESS IDENTIFIED AS SOME OTHER LOCATION. SOUTH SEA PEARLS ARE NOT FROM JAPAN. IT WOULD BE BEST TO QUESTION THE FAMILY WHO BOUGHT THE RING AND ANYONE WHO MIGHT HAVE INFO ON IT. THAT WOULD BE THE MOST RELIABLE INFO ON THE RING. GOOD LUCK.

PETER