Those old Deltas have what I think is the best blade clamping system ever. That particular model has the Quickset clamps top and bottom. If both clamps are intact and everything else works as it should, then it's a very good saw. I would definitely buy at around the £50 mark but if in very good condition probably go to £100. Spares are hard to come by but don't let that put you off, a lot of things can be worked around except the clamps, they are as rare as hens teeth. I have a 40-560 that is 25 years old and is still going strong although I've had to do some lateral thinking on replacing some of the parts that wear out.