it's possible that this coin is forgery, but why someone used uknown moneyer name? or why it's triple striked? and why there are no other simillar coins out there? if it's a copy coin than there should be at least few known examples.
Quite a lot of hand struck forgeries are 'unique' - and given what you paid for the coin, I'm sure even striking one would more than pay for the effort to create it.
Sometimes forgers use techniques such as bad multiple strikes so that people say - 'this can't be a forgery, they would want to make it perfect' - but there's probably a greater number of people who would jump at the chance of a coin that should be >£10k for £600 than a collector willing to shell out £10k+ (although there are plenty of forgeries at that level too).
I'm not saying that yours is of course, just pointing out why fakes are often unique, not struck well - and of course by making up the name of a moneyer there are no other examples to compare the style to - and any little differences can be put down to the 'unique' styling of the otherwise unknown moneyer.