Cartridge without serial?

Actually a serial number itself if not a warranty, you can get warranty when you’re buying from official dealer and it’s dealer ship your cartridge to the manufacturer (not you).

Grey market seller often erase serial numbers or replace them with fake serial numbers, so the manufacturer can’t track the source.

I have serial numbers on every cartridge I got in my big collection of cartridges, except for one ZYX Airy III cartridge purchased from 2juki from Hong Kong! Upon my request the manufacturer confirmed it was a fake serial number, so no warranty!

As been stated million times on this forum:
Refurbishing some special high-end cartridges using different parts from re-tippers is a bad idea! 

Manufacturers of ultra high-end cartridges never refurbish or re-tip them, with warranty you have trade-in program to ship your old cartridge back to get brand new cartridge (even next model) with special discount. 

Rdk, you nailed it right on the head. Reviews are telling and I'll take it risk. After doing some digging I'm going ahead with purchase. 

I have serial numbers on some of my cartridges.  The Kiseki Blue NS I bought from Kron doesn't have one.  I did a Google image search and couldn't find an image of one with a serial number. 

Generally speaking, if you buy an "international" version of something, it's not going to come with a US warranty.  As long as the seller has a lot of positive reviews and you have a level of comfort that it's an authentic item, I think your risk level is relatively low.

What cartridge @j-wall ?

Chak, in one paragraph you contradicted yourself. You wrote that your ZYX aiRY III cartridge lacked a serial number, and then you also wrote that it had a fake serial number. You can’t have that both ways. Which is true? And this is the umpteenth time you have brought this up, so I gather you are really pissed off at 2Juki.

It’s not like anyone with a bona fide expensive LOMC  cartridge is going to get anything approaching a good deal when he or she goes to have it re-tipped by the manufacturer. In general the net cost is similar to that of a brand new cartridge. In fact, as you know, often what happens is they take your cartridge and send you a new one. In other words, the so-called factory warranty is essentially worthless.  People go to aftermarket retippers to save large sums of money vs having the retip or exchange done by the manufacturer. Yes, the trade-off can be altered SQ of the retipped cartridge vs the original. However, it is often the case that the customers are very happy with the results. Live and let live is my philosophy.