If it's just normal metal You need to regrain it...which just means sandpapering it.
If it's shiny chrome only use Novus 2 on it...although in a ball return area it should be fine for sandpaper.

Would you not suggest using a metal/chrome polish? I've used Mother's Mag Polish and Brasso with very good results. I usually try to stay away from abrasives as much as I can.

As for the small paper decal that goes in the trough, Pinball Resource sells them on this page here: http://www.pbresource.com/signatur.html

They're only $2 each. Ordering one would also be a good way of establishing an account with them.

https://pinside.com/pinball/forum/topic/regraining-metal

Here are some other thoughts as well.

Hey if they work and you got'em that's cool too. I'm personally drawn to using abrasives, might be my personality?
I've never actually done a trough...usually it's ball guides and for me some quick sandpaper id just as well.

No problem. Just be forewarned, the pinball resource does an old fashioned way of business. You have to establish an account with them, order a small parts order (first one is less than $10, I think), he ships you the goods, then you send a check in the mail with the remit copy of the invoice that's sent in the package. It's a little awkward at first, but he's a treasure in the pinball industry, especially if you're into Gottlieb games. His parts and services are invaluable, and his prices are often the best out there. There's plenty of threads here you can search for if you need more assistance ordering from him.

Eagle One Nevr-Dull is a great metal cleaner/polish.

Gottlieb games of that vintage will have a schematic, which he will have, but no manual. They didn't start manuals until the 70s

It certainly grows on you! Once your one game collection grows, and you make larger orders with him, he gives you a 10% discount on $100 or more. Just enough to cover shipping, and a little bit of tax. You can't beat it. Just make sure you include the part numbers in your email order (or phone call order). The part numbers are always listed along with the product on the website. It's an awkward process, but they're damn fast, so it obviously works well for them. Good luck!

That's great to hear! I haven't called but emailed all my old orders. Steve and jimmy have helped me out and know so much about gottliebs it's great!
I actually like writing a check to them. Keeps it old school

They are a very good company to deal with. Here in England, its not quite as simple to order spares from suppliers though now PBR accept an on-line payment system, its now very easy to do. Before, I had to send cash through the mail system which of course is highly risky though I never lost any money!

Anyway, let's be grateful for such firms helping keep the hobby alive.