5 Shillings Zuid Afrikaansche Republiek 1892

Recently a friend of mine at work brought me this coin and asked me to sell it for him. He got this coin, left to him by his late father in Malawi.

This might seem like an easy thing to do. Take pictures, make a price and post it on eBay, Facebook marketplace or Gumtree.

Yet as I looked at the information available at the three sources below, I realized that I do not know enough.
Source 1
Source 2
Source 3

There are single and double "shaft" coins. What does this mean?
How do I know which is which? I can't seem to be able to google that answer.

The next question would be, do I try polishing the co myself? Now I know you don't just rub it until it is clean. I do have access to some fine-grit lapidary pastes ranging from 3000 grit diamond paste to 100,000 grit diamond paste and cerium oxide which would be for putting a final polish on stone and gemstones.

The final question would be where to sell this coin? Looking at the prices, I do not have the money to buy it and keep it, which is my go-to response with these things. However, my friend has decided that he needs the money and will pay me a generous percentage of the money made in doing so.

So over to the Hive Community. Lend me your expertise!