Look at completed auctions on eBay (I usually filter for "sold" - I don't need to know about the failed auctions). I just had a quick look, and prices seem to vary a lot. If you're not familiar with how to do this, establish an account there (free), then click on the "advanced" link to the right of the search box. Search broadly: Van Dorn drill. Narrowing it down will miss the auctions that were described badly.
There's also Worthpoint, which accumulates years worth of online sales, but I believe that costs money to subscribe.