There should be a rope attached to a long lever up in front of the seed box. Pull it once and it drops, pull it again and it raises. If not you need to take apart that round clutch type deal that has the notch in it. May be a broken dog or spring or it could be just so packed with grease that it can't work properly. Those old JD-Van Brunts are really good drills. Yours looks like it has the horn type open seed depositers (Model FB-A). If so it will only do a decent job in a prepared seed bed. If you can find a "B" model it has a double disk opener and will work well in a prepared seed bed or in grass like pastures etc.