It’s quite easy to turn pennies silver or gold - high school chemistry. See for example: https://www.sciencecompany.com/Turn-Copper-Pennies-Into-Silver-and-Gold-Pennies.aspx
The gold isn't even the issue. I could really care less about that now. I'm just hoping that it comes thru as a mule. The fact a coin is on another coins planchet does make it a mule correct? You can see the torch on the back, twice actually. They cross like rifles. The coin isn't in bad shape like you think from looking at the pics. In your hand it looks smooth and glass like on both sides with not even a lot of scratches for real. The coating of whatever it is that's on it has done a great job at keeping it from going further into decay. O and those other gold coins on eBay are just fake like toys. This one you can actually see there is a dime inside and even imagery or whatever you want to call it from the Sacagawea gold dollar. The Indian standing by the horse and the girl with the lil one on her back.
It's not on another coins planchet. If it were a dime planchet, all those letters would be halfway into the edge. It's not gold plated, it's not brass plated. It doesn't have the reverse of a dime. In numismatics, a mule is a coin or medal minted with obverse and reverse designs not normally seen on the same piece. These can be intentional or produced by error. This type of error is highly sought after, and examples can fetch high prices from collectors. Your coin is not a mule. In paper currency a mule note is a piece of currency that has a back plate number that is a different size from the front plate number.
What on earth does a Sacagawea dollar have to do with this coin? They didn't even make the Sacagawea until 7 years after this coin! This is just a normal beat up circulated Lincoln cent, nothing to do with a dime, a Sacagawea, no British 2 pence, no British Gold coin. If you don't like the opinions, send it in for authentication it is your money.