1846 Half Sovereign?

Hello, I have what I think is a gold half sovereign, but it seems much paler than other sovereigns I have. Weight is 3.92 gm and diameter is 19 mm approx.

I'd love your thoughts on its authenticity:

Gold should not change color that way.

Metal purity/detection kit costs around 1-2k USD. Maybe take your coin to some goldsmith and ask them if they can verify that it is gold without destroying or damaging it.

 The original coin - N#23736 

which yes is 19.3 mm which rules out inclusion in 

N#41074 

which is for Young Head coins but made in miniature, 

plus they have Lauer on them. 

 Leaving a maybe brass item which, around 180 years ago had gold plating 

on it, to deceive shopkeepers into thinking it was real. Well, those that 

did not have a coin weight device. Just guessing all that though. 

Density measurements can be done easily and cheaply at home and accurately enough to tell the difference between 18 g/cc and 9 g/cc.

https://en.numista.com/numisdoc/determining-the-metal-of-a-coin-27.html

Thanks for all your comments. I'll try the dentisy measurement and let you know :-)

In the end I took this to a local jeweller. Two of their staff looked at it. They agreed it was a half sovereign, but quite worn. Thanks for everyone's comments.