Alamein, welcome to the board, glad to have you join us.
If you can provide good clear pictures of the markings and a close up with that crown it would help, another clue that sometimes helps is to tell us what country it is in and what history is being credited to it...not always correct by the way, usually interesting but can help.
Oh yes on the internet typing in all caps is reserved for yelling. Since I got my new hearing aids, I can hear just fine, wife says there is still have some issues with listening...bah on her. Reading all caps is hard, so please turn you cap lock key off.
In banner at the top of the GBO page you will see the word search. Click on that. The search window will open. When it does look for advanced search and click on that. When advanced search opens type in carronade in the search for window. Below that a bit you will see a Choose a board to search in, or search all section with a box that has a checkmark for search all. Click on the checkmark by search all to remove it, then the click on the plus sign by Choose a board to search in, or search all title and list of of the all the boards on GBO will open.
Near the top on the right under Black powder forums Click on the box by Blackpowder Mortar and Cannon Sponsored by Seacoast Artillery, then scroll to bottem and click on search. I got 3 pages of post on Carronades.