1857 Sydney Mint Sovereign

"Mule" is not a synonym for "error". A mule is where the die from one coin is accidentally used to make another coin it was not intended for. (such as a 10 cent die used to make a $1 coin, or a sovereign die used to make a shilling). The error (or rather,"variety") you are describing is known as an "overdate".

First up, you haven't told us the denomination; both half-sovereigns and sovereigns were struck in 1857. However, there is no 1857/5 overdate listed in the catalogues for either denomination, but there are plenty of other overdates in the series. We'd need to see a pic to see if you have an unlisted overdate variety or just strange damage that resembles an overdate.

if anyone want to see the 1857 with 5 under the 7 can view it at fitzroyfallspottery.com under coin folder as I have a website I sell pottery from.
I also have a 1927 canberra florin which has 2 rims like a mule and might be a proof as the details are clear and you can see the 3 steps going up to the parliment plus heaps of detail.

Here's the pic from your website:


I can see damage on the 7 and 5, but can't see an overdate.


No. A coin made by using an older coin as a blank is known as an "overstrike". However, the scenario you give is unlikely. There is no reason why the mint would take a perfectly good two-year-old gold coin and overstrike it. If the old coin were worn or defective, it would have been melted down and made into fresh blanks. It's also highly unlikely that if such an overstrike occurred, the 1857 design would line up exactly with the old 1855 design. In coins that were made by overstriking an older coin, the undertype is oriented randomly.

After reading a article which talked about this coin I went and checked mine and found it under the 7 my coin is better than the one in the article as you could only see the part below the 7 on the left middle where at the base on the left of 7 their is still traces
I am not just being wishfuk thinking as I dont need anymoney in life and am only corncerned with the history and rareness of the coin, I like discovering, I once found 24 old parish maps from the colony that were thrown out by the DMR years ago and no one would believe the maps were important, took me years to prove it then the government took them off me claiming they were theirs when they did not want to know when I tried telling them they lost important maps.