Question on Vintage Mikimoto Clasps

[amti]

When did Mikimoto first start using his current swirly decorative ribbon clasp? Does it date back the the 1960s? Most of the clasps I have seen from the 60s are silver and not the ribbon version. I'm curious because there is one for sale from 1966 and it is silver. I have no intention of buying it, but I'm curious. I think the paperwork is authentic. I've never seen blue baroque akoyas with a silver ribbon clasp dated that old.

http://www.ebay.com/itm/162328039629?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT

 

[Camelotshadow]

Pictures are gone but I do seem to recall a vintage silver ribbon. It would be marked SIL not sterling.
I have the restangular sil clasp with pearl on a 60's strand.