I have a 1960 D17 diesel. It did not come with the valve that you describe. Sometimes these were added when they put a loader on the tractor. Sometimes they added a front mounted pump at the same time so that there would be full time hydraulics. Where are the hydraulic lines hooked to the tractor? It would help enormously if I could see pictures of where these hoses connect to the pump (or tractor body).
If you are adding a 3 point conversion, these valves will not be used at all. The cylinder for the lift arms is inside the transmission case. Lift for these arms is controlled by the bottom lever on the steering column. The top lever is for the traction booster.
If your main interest is a three point, these valves may prove to be useless - but they are useful. If you don't need them and want to remove them because they don't look nice or are in the way, you can sell them easily. I've been thinking of converting my trip bucket loader to full hydraulics and would need a valve (and hoses) like this to do that.
I can help you with pictures of a 3 point for the D17. I put a category I on mine for use with a bush hog and a scraper blade. The design I did cost about $80 and you can do it yourself with a little welding. It is also removable and doesn't require any welding to the tractor - it bolts on. I removed it recently and put it on my D-14 (fit without adjustment).
I'd like to hear from you. Your email address didn't work for me.