u/Various-Crazy4894

I’m trying to determine whether this coin is authentic.
It’s supposed to be an Augustalis of Frederick II, minted in Sicily around 1231.
Previous photos had very poor lighting, which made the coin appear silver. In hand it is clearly gold.
I will also upload a video shortly.

Specifications:
Composition: tested at 20.5 carat gold (~85% Au), which matches the expected composition
Diameter: 20 mm (expected range: 19–21 mm)
Weight: 5.30 g (expected range: 5.15–5.35 g)

minted in Sicily around 1231. Do you think it’s authentic or a fake?
How can I tell if it’s fake?
The weight, composition, and diameter match the expected specifications, but I assume those are also the easiest things to fake.