I took the mast boot off the keel stepped mast of my Yankee 30 sloop. I discovered what appears to be a splice in the mast

. About midway at the partners, there is a horizontal joint in the mast with several rivets above and below it. I can only assume the rivets join the two sections of mast to an inner sleeve. Has anyone heard of anything like this? If so, what would be the purpose of the spice? Someone suggested that the mast might have been tabernacle mounted at some point, but I find this hard to belive in a boat that was designed to be keel stepped. In addition, I see no signs of a tabernacle on the deck. Any ideas?