Looks good to me Lamsdorf. These were made when the value of the coin was equal to the value of the metal it was struck from. Copper was cheaper, so the coins were bigger!
Needless to say they weren't terribly popular as they were inconvenient to carry around. Many were saved as souvenirs such as yours. However many suffered damage at the mint. They were large and heavy and dints from other coins as they were bagged up were common. Yours seems to have escaped that.
Nice example. Looks to be a genuine coin to me.
There are a number of different varieties depending on the number of leaves/berries in the wreath on the King's head/ portholes on the ship. And patterns as well. However I have no experience of the series so can't say more than that.
Hopefully one of the experts will be along later and can give you more info. Were there any details with it? Where it was bought or anything?