View attachment 1926931 this button was about ten feet from the eagle.
The boatswain can be identified as a petty officer by the presence of the eagle and anchor device of 1841 with the star above it, prescribed in 1852. It would not be until 1866 that a system of rating badges would be introduced, so we can determine this man’s rating only by the all-covering petty officer’s device, worn on the right arm and the boatswain’s pipe.
I may be looking at this wrong but I don't see an anchor. I see a sword hilt.