Koestu original Onyx Sig pre-platinum cart vs. later/current platinum Sig comparisons

I’ve recently acquired a previously owned Koetsu Onyx, but would like to find out more about its vintage. It has black blocks with unthreaded mounting holes and a black upper side with ‘made in Japan’ and ‘18333’. No P before the serial number. Is it correct to assume this is a pre Platinum version, or are there platinum versions without that P? The box only has the three letters ‘PLO’ handwritten in pencil. With some fantasy this might indicate PLatinum Onyx, but obviously anyone could have scribbled this on the box. Does anyone here know what version this might be?

I have more than 30 cartridges but this is my first Koetsu, believe it or not. I was not impressed by hearing a Rosewood in my own system a few years ago. So I lost interest in the brand, for a while anyway. While this Onyx sounds much better than my memory of the Rosewood, I’m still not overwhelmed. Any tips on getting the most out of it?

PS: I followed the general consensus and started with an FR64S with SUT (Ortofon T-3000). When I moved it to a Micro MAX-237 with solid state mc phono amp it opened up and sounded more powerful and dynamic. Anyone tried it with current gain phono amp?

I have had good success with a Rosewood Signature Platinum on a FR-64S.  The pre I use is a Pass XP-27 which I preferred to a SUT/MM input combo.  Not sure about how one dates a stone body Koetsu.  Did you have a chance to examine the stylus with a microscope?

@edgewear

By now I’ve seen pics of several slightly different pre-Platinum Onyx short bodies; it’s almost impossible to say exactly what you have, unless you get in direct contact with Koetsu. Still so much mystery with Koetsu!

I don’t personally know of any Platinum Koetsu that doesn’t have a leading "P" in its serial number, but that doesn’t mean it can’t exist. There could be pre-Platinum Koetsus that were later rebuilt with Platinum magnets (with original top plate retained).

You might join the "Koetsu Users" Facebook group, which has some interesting vintage Koetsus posted & discussed by members. These groups have the advantage of easy image inlining.

In a revision of my previous comment on this thread, I would now estimate my non-platinum Onyx at between 0.4 and 0.5mV output. Not fully double the Platinum model’s 0.3mV, but still quite noticeably higher. I would guess its magnet is most likely samarium-cobalt or permendur (i.e. like the Black, Rosewood, and Urushi models). The fabled long-bodies should use alnico - very large alnico magnets were necessitated by the (relatively) weak magnetic material, which required the long bodies to house it!

As to sonic matching - I absolutely prefer all my Koetsus with EAR SUT (or Koetsu SUT, or Quadratic MC-1 SUT) over any active MC stage, including that of my ARC Reference 3SE. FR64S and 64fx arms here. But then, every system is different! 

Not sure about how one dates a stone body Koetsu.

Carbon dating?

Platinum magnets are like green eggs and ham.

I do not like green eggs and ham.

I have dated numerous Koetsu's over the years, and the allure has waned with the passing of the old master and the advent of platinum magnets.