no, not really.
they are usually stamped on the back of the arms with mx 1000, or mx 900 but it seems on some early ones, they are not stamped.
if they have got the stamp, weinman adjusters, and quick release levers, you probably wont go far wrong for 40 quid though, you'd pay 20 for a set of fakes, so at the worst youve lost 20 quid.