Rusty gold sovereign?

I was flicking through an auction catalog an spotted this item

https://capesdunn.atgportals.net/auctions/8287/srcap10391/lot-details/dda1d16a-d6ef-4563-92c7-af03011309e3

I have never seen rusty gold, is this a fake?
Or do sovereigns of that era contain other metals?

I’ve never taken much interest in sovereigns.

SanMarino wrote:I was flicking through an auction catalog an spotted this item

https://capesdunn.atgportals.net/auctions/8287/srcap10391/lot-details/dda1d16a-d6ef-4563-92c7-af03011309e3

I have never seen rusty gold, is this a fake?
Or do sovereigns of that era contain other metals?

I’ve never taken much interest in sovereigns.

Sovereigns are 22 ct gold. This is my biggest problem with buying them. They are prone to having issues but this was most likely in a wet environment. The other metals are usually copper and base metals to make up the weight. 

This looks real, and needs a clean. But I wouldnt touch it personally. I would rather buy pure 24ct gold.. IE the newer Brits  . or Maples.

Sovereigns, Krugerrands and US Eagles are 22ct and contain an alloy of gold, copper and sometimes silver. The new Sovs don’t have the silver, hence why they are more of rose gold pink colour. These other metals can oxidise and create spots, but won’t affect the gold content.

https://www.bullionbypost.co.uk/index/gold/does-gold-rust/