Age of Mikimoto Tokyo pearl pendant

[Ricepudding]

I have a beautiful Mikimoto 14K plumeria pendant with center big pearl. It is marked Mikimoto Tokyo and the M inside clamshell. Does anyone know the year(s) this Tokyo hallmark was used? I'm trying to determine if it's new or vintage. Thank you in advance.

 

[whitewave]

Pic please