They're probably worth, dependant on the age and condition, about the £50ish mark i'd presume?
They've got such things as better build quality, metal mount, distance meter etc, whilst look at the mk2, it's 99% plastic.
For the price, it's probably worth getting one, and seeing what it's like, and comparing the two yourself.
Neither are goign to be expensive, and whilst the mk2 is absolutely sublime for the money, i'm presuming that there was something to improve on, as they brought out a mk2.