My scoring was around the 'male' half of the joint, if that makes any sense?, and I assume one the inside of the female portion of the join (although I must confess I can't remember ever looking). It was like the anodising had just worn away and instead of the grey coloured coating, it was bright burnished metal, And looking closely you could see small scores and scratches. I did use it a
hell of a lot, and for a couple of years. It's at least 4, prob closer to 5, years ago that I bought it. And lost it maybe 18months ago. So I don't know if their manufacturing/anodising process might have changed since then if my
problem experience is uncommon (I say 'problem' - it never really was, I just bore it in mind when replacing it).
The O ring is neither here nor there really from a functionality (output) point of view IMO, but it did seem to feel a bit 'smoother' turning than the Nano without one. But if I had a dodgy anodising this could also account for that in part. The magnet is bit of a better benefit in that you can actually drop the grinder in use and it doesn't fall apart. Not sure how often that scenario would happen empiracally though, and even if it did there's not a lot of bud in there to be lost anyway. But nice to know I can drop it if I want, I suppose...
Regarding the colour- I did pic up a 30mm no-name CNC- it's in my pics next to the 'Head Chef'. Exactly the same production by the looks of things, but without the colouring or logo. Same grind in the end. It was about the same price too, from my LHS.
I think M&B are just a bit more expensive this side of the pond- if I remember right I paid 15 in my LHS for my original Nano II 4-5 years ago...... which was a lot of money back then
So for me here having tried the non branded versions I can no longer really justify the extra, but in your market without a premium then there's not really that much to differentiate between these 30mm grinders IMO except the o ring and magnet. And that has little bearing on the result anyway.
EDIT- I just had a look at the M&B website and it all came flooding back to me. I did try to order a replacement (plus a load of other grinders) from them after I lost my Nano II. Ended up falling out with the fellow there 'Dan' via email- turns out that massive logo they have at the top of the page saying 'WORLDWIDE FREE SHIPPING' actually means free shipping in the US only with orders over $80. I obviously didn't pay enough attention in either English or Geography classes at school. And it's still there on the website all this time later.... I'm not sure how they can get away with such misadvertising?
But at the end of the day they have pobably lost my long term custom from that chain of events.