I have a v12 engine qeustion?

My uncle has a custom mercedes that he bought and it had a v12 engine but that speedometer or what ever its called(yes i know its stupid to not know it). but the highest number on it is 160 mph does that mean he cant go go higher? because for v12 wouldnt it go faster? actually i think the top speed could have been 200 mph i think? lol i forgot but how fast do you think it could go?