The fact that it is hollow with removeable ends suggests to me that it was a courier device used for the secure transmission of messages. Similar devices, often ornate silver, have been used in India in the 18th and 19th centuries. Just guessing, but the style looks early 19th century. Don't think it has anything to do with the rank of the user. While the US Army / Marine Corps have a tradition of swagger sticks, they normally are not indicators of rank.
What makes you think it's American other than the eagles?