Batavus bicycle cassette information?

If the bike really does have a cassette and not a freewheel, the rear wheel is probably not original equipment. If this is the case, you will have great difficulty locating a replacement cassette. Those old style cassettes are no longer made so you would have to hunt for some place that has some 40 year old cassettes hanging around. You would probably have to buy a complete new wheel made for a freewheel which is probably what was on the bike when it was new. A new chain will work fine on the cogs that are not worn, but it won't mesh with worn cogs. With old cassettes, the cogs can be reversed, freewheel cogs can also sometimes be reversed. If you can do this, you can double the lifespan of a cassette cog. However if your cassette is a newer hypergilde design the cogs cannot be reversed to extend their lifespan. As for the value of the bike, it is only worth as much as a prospective buyer will pay. If the rear wheel has been replaced, the bike loses value since it is no longer as it was when it was sold. If by chance the bike has a Maillard helicomatic cassette hub you are really out of luck, those things are really rare and hard to find. You would probably have to replace the wheel.