Cartridge without serial?

@mammothguy54  You make an interring point. Is it possible that the cartridges in question, Zyx's, Benz's, Koetsu's and others that are being offered from these grey market vendors are in fact knock-off's? This would certainly explain the lack of a serial number and the annoyance of the very small manufacturer who apparently has logistical stock control.

It is indeed possible those cartridges are knock-offs.  However, it's impossible to know for certain unless you bought one and then sent it to the manufacturer for inspection.  Even a serial number can be misleading.  Our products (of the company I worked for) were being transshipped and the "rats" were placing phony serial numbers directly over our laser etched serial numbers on the chassis.  The end-users didn't know the difference.  Here is a good story... Taylor Made golf clubs were having a high rate of return/defective/failures whereby the shaft was breaking on their drivers.  They have a very high standard of excellence and do extensive testing prior to releasing a product to market.  With such a high and unusual rate of failure they began to research the returned clubs.  On the outside, examination, they sure looked like their products.  However, when researching and testing the metal alloy of the shaft they discovered it was not their product after all.  Contacting the end users they also learned these clubs had been purchased from unauthorized sellers.  It seems those sellers were securing their inventory from a knock-off vendor and, thus, were able to sell the clubs at highly discounted prices.  Did the consumer (end-user) really get such a good deal after all?  I think not.  If the price seems too good to be true then that is indeed likely the case.  Moral of the story, you will be fully satisfied buying from a reputable authorized dealer who sources their products directly from the manufacturer or authorized distributor (depending on the manufacturers business model).  You can almost always get a respectable discount on the product with a simple request or comfortable negotiation if the product is being purchased with other items as well.  And you will have that authorized dealer to help you in the event there ever is a product issue (even Rolex has a service department).
I hope this helps everyone in their decision making process.

Here is a good story... Taylor Made golf clubs were having a high rate of return/defective/failures whereby the shaft was breaking on their drivers........

Wooow...unbelievable!

@mammothguy54 I had heard the story about the Taylor Made clubs before. OTOH, it is interesting that there could be a company doing ’knock-off’s’ of cartridges like the Koetsu’s and the Benz’s. Albeit copying a cartridge could be a relatively easy enterprise, assuming that one had access to a manufacturing facility that knew how to make cartridges...and could deal with the very small parts etc., While I don’t believe there is a very large market for ’knock-off’ high end MC cartridges, compared to Taylor Made clubs ( as an example), I guess if the mark-up is there??

@mammothguy54 what a stellar example. Thanks for the insight.