What you have is an older frontier ss1023b spreader. I just saw the same spreader with theexact same gate design online. The primary difference is the top link attachment you have is a single hole design and the new ones have double attachment holes for the top link. Restoration will consist of ensuring the drive shaft and gear box is packed with grease( not oil) and the remainder is cleaned up and product flow adjustments in the gates are proven free to move. Go buy some green John deere tractor paint and it will look like a new frontier spreader! Have fun!
I have the ss2036b unit and I think it's great! You're missing the product flow rate stickers but inputs not that hard to work out. Look at new ones and copy the charts. Don't bother trying to hunt down the owners manuals in my opinion, they add little value. You will find how to videos and posts on here that should guide you. One downside of these smaller spreaders ( mine as well) is that they are not quick hitch compatible but they attach to the three point hitch easily enough.