I tried this question on another forum & no luck.  Maybe someone here knows.  This may be a dumb question.  What’s with all the mk II & mk III stuff.  I see it on various brands & an equally varied type of things.  Turntables, my new phono preamp & cartridges.  I’m pretty sure I saw an amp & some speakers Both for sale here. 

I’ve googled & did a thread search here. I can’t find anything that explains with at it is or makes something an “mk” let alone a II or III.

Unless... My Kryptonite?? Some of the stuff I see makes me weak in the knees, my head spins & I drool profusely.  There’s also a Lincoln MK II but, I’m just throwing that in for fun.

I’m really curious.  Thanks for sharing your knowledge.
It is quite simple. It means updated.

MK is short for "mark" which is kind of like "brand."

So MK III is newer than MK II which is newer than the original.

Originals, being original, often don't have a "mk" nomenclature, like during Julius Ceasar's lifetime, he was not Julius Ceasar I. He was just Julius Ceasar.
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New! Improved! Some companies offer updates to current models only occasionally, others as a regular means of generating income between new model introductions. Another designation is SE, for Special Edition, often the final version of a model.
Mark II, abbreviated mk II, is the second variant of something. mk III is the third variant.

From Wiki:

Mark II - Wikipedia
Mark II or Mark 2 often refers to the second version of a product, frequently military hardware. "Mark", meaning "model" or "variant", can be abbreviated "Mk.".