E30 Zone

I've been offered some cams but have no idea if authentic or not.
Does anyone know how to indetify them to ensure they are US spec and what to look for to determine condition?

Only way to tell is by the difference in lift and duration

Cheers Dan,think I'll give them a miss.They are miles away and is just some random I came across who said his mate was selling some.Too large a gamble for the price.