Buffalo D/P's are great, solid machines. I've had a 15" 1950's era Buffalo bench drill for over 30 years and recently passed it along to one of my sons who is setting up his own shop. My guess is that the counterweight is cleverly shop-made. I've never seen anything like it on a Buffalo. The head on mine is moved by hand-no rack or counterweight. You've got a nice old machine there.
Tom B.