Information about Koetsu please ...

No answer ?

I think modern koetsu cartridges include a "P" prefix before the serial number eg P124 , if they were constructed using platinum magnets or whatever . If a cartridge is said to have been upgraded to platinum status then it should come with a certificate signed by Fumihiko Sugano stating this .

I once owned both an Onyx,and then an Onyx Platinum.I don't believe they looked any different,at the time,except in my case the Onyx Platinum had a more beautiful Onyx body.Of course this is probably a unit to unit variation....But...

Sonically I DO remember the "PlATINUM" to be the better sounding design.

Hope this is of some help.No doubt you'll get more up to date info from some others.

Best

My Jade had a P before the serial number, so my guess the Onyx Platinum is w. a P before.