I'm still not sure exactly what info you are looking for.
The cobra is just an updated K, works exactly the same. They changed materials and did some slight design modifications inside.
From what I can tell, it was done simply because the original patent ran out. Just before the cobra's came out, a whole wack of knock-offs appeared on the market.

We don't kit lock-offs or vapourizers any more. It's cheaper to just replace the whole thing because of labour.