mbk is the name used to refer to a model of vintage submariner that can accept gen parts, the name is derived from the store in which they are purchased in asia. once modded up they are very close to a genuine watch of the same model costing far less than what other case manufacturers would charge you ($500-$1000s less) for the same quality. you would really only buy the higher retail cases if you wanted to fit a genuine movement with out having to sand it. other than that they still need modding to be accurate.
a quick example of a 5513 once you drill the lug holes, trim the cgs, install a new insert, and refinish the dial.
i often sell my modded pieces once i get bored with them and sadly no longer have the one above in my collection, but i have new pieces to play with and mod (until i want to fund new projects and sell those)
MBK/MBW (interchangeable namesake from the before time) also makes a sea dweller (1665)
they are fantastic watches , but require modding and stringent quality control before they can be (or should be) sold.
I am no different than JMB in the fact that i do mods and build some mighty fine 5513s, and 1665s
*we should really create a wiki