Nice find!
I'm pretty new to Duals so I hope more experienced AK:ers can help you out.
But here's some:
A previously never used unit is certainly a good start. You don't have to worry that any prevoius owner has tinkered with it.
But it has been sitting for 40 some years so you probably want to clean out old lubrication and add new in the right places before putting it into operation.
There're manuals free to download overover
www.vinylengine.com of you sign up for membership. There's also a large and helpful Dual contingent over there.
Also: if some buttons or levers are stuck don't force them! it might be old grease that has turned to glue that makes stuff stick. Force and things may brake!
It's a belt drive so a new belt may be a good idea (but old belts can work fine too, it does on my 601).
Finally: there's a small but crucial part called "plastic guide", "steuerpimpel" and some other names. It's needed for the automatic tone arm movement.
These guys almost always break/crumble on old duals. But they are cheap to buy or DIY. Also an easy job to fix. If the arm doesn't move right this usually the cure.
And of course: there's probably an unused cartridge and stylus that will work fine. But is it in a store box it might not have been fitted yet.
Now let the experts speak. Maybe someone has a 1257 and can give you more specific advice.
Good luck with the new deck and hope it arrives safely!
