Help Identifying Koetsu Onyx

Never seen any stone body look remotely like that. I have both an old non-Platinum Onyx Signature, a low serial-number Onyx Platinum, Coralstone Platinum, and Jade Platinum, lol. Platinum serial numbers start with a "P". Older Koetsu builds don’t have threaded mounting holes, and older still will use gold pins instead of silver. Older still, and you get silver top plates (like my Onyx Signature). And long-bodies go even further back than all of those. The top plate, mounting holes, and pins are not changed out by Koetsu on a rebuild (I know because I asked for it and they wouldn’t change it).

I think (but cannot verify) that any genuine stone body with threaded holes and silver pins would be recent enough that it would have to be a Platinum model (all stones became Platinum at some point), and should have a "P" serial number on the top plate. Your pictured example violates this, and furthermore it features the simplified gold cover/guard plate without a raised "lip" -- which is a feature exclusive to the modern entry-level Black and Red (Rosewood Standard) models.

So I think it has to be considered a strong possibility that someone shoved the guts from a modern Koetsu Black/Red into an Onyx shell (which itself may or may not have been genuine Koetsu). Either way, sadly there is about zero chance that this example actually has Platinum magnets. It might still sound very good, if the guts were genuine Koetsu and have not been unduly worn or tampered with. But if you were sold a Platinum, I think you did not get that :(

I'd be wary. (don't know how much you paid)  For this kind of money you want it right.

I agree with most of the comments here. The shape of this is similar to the current Black and Rosewood Standard.

Having seen a few Onyx Platinums before, I have never seen one like this. Nor have much older non Platinum Onyx looked like this. 
I believe Koetsu have/had fairly recently a non Platinum Onyx available again, but I've never laid my eyes on one.

I am thinking there are 2 possibilities then:
1. It is a non Platinum Onyx (or Onyx "standard") of late production, which I can't verify as I've never seen one.
2. It is not genuine.

Either way, sorry to say I don't believe it is an Onyx Platinum.

Thanks for the comments. 

There are 2 issues here. The first is whether the cartridge is authentic and the second is assuming that it is, whether it has platinum magnets.

I bought this off a reputable second hand dealer in Japan. These things go fast in the Japanese used market so I pulled the trigger quickly. I've always wanted to own a Koetsu stone body but the retail price for a brand new cartridge is too prohibitive. Frankly, I didn't notice the missing cantilever cowl and the tapered front until the transaction was done, at which time I started doing some searching on the web but couldn't find anything useful. 

I did manage to find some other similar looking examples on the used market:

https://www.vinylengine.com/turntable_forum/viewtopic.php?f=19&t=98006

https://page.auctions.yahoo.co.jp/jp/auction/282949853

I also found a Korean blog about a similar looking cartridge:

http://blog.naver.com/PostView.nhn?blogId=imjbler&logNo=150081760337

http://cy.cyworld.com/home/28868771/post/3504472 

I realize that there would probably be no absolute certainty on the provenance of the cartridge unless I send it back to Koetsu for a rebuild. I haven't had the chance to mount the cart so I will see how it goes.

Also, I found this article talking about the history of Koetsu cartridges. Appears to be translated text but I couldn't find any information on the source:

http://fs5.directupload.net/images/160608/24ta43zq.pdf

Wow, things are looking up again! Koetsu history is just so damn shrouded in mystery. And just when you think you've seen them all...Forgive me for my uninformed prior post. And thanks for posting your findings.

That would be really cool if it is indeed a limited-edition Onyx Platinum. Such a gorgeous Onyx grain on your example, too.