In the medieval world, europe at any rate, trades were dominated by guilds. They determined the rules by which they worked, the skills taught, and who got accreditation. To be a master of a craft took a lot of years of work, creation of a masterwork item (that other masters recognised as being of sufficient quality), and likely some buttering up of the senior types as well.
Indeed some have theorised that Free Masons have their roots in the Stone Mason's guild, who allegedly had secret words and hand gestures so as to determine who on the building site were legit or not.
Nowadays anyone can call their business pretty much anything, and boast of skill levels they may or may not have - including that of "Master". It gets worse. Insert trade here + King has nothing to do with royalty, but chances are a crown motif will be incorporated into their branding. As a comedian I heard on Martin Malloy once noted Insert trade here + Aardvark is not an indicator of said animal being employed but is just a means to get the top name in the phone book because of Donkey Voter yellow book users.
Whilst on the bus this afternoon, engaging in some light Air Jabeling (singing silently along to Tenacious D's Tribute and doing the expressions / gestures as per Jack Black from the film clip), I noticed a van go past at the roundabout.
The van belonged to 'The Framing Master'.
In addition to guilds, the Master title has been embraced by popular fiction in relation to martial arts "cults". 'Hard Master' and 'Soft Master' for example were members of Storm Shadow's Ninja family from the GI Joe comics.
Naturally this is the first thing I thought of. They should totally use this as their branding.