Early shipboard bowling ball

This was dragged up by a trawler in the Gulf of Maine. We did some online research, and a few nautical antique people. There are a few of these around, and I've been told it was used in an early form of bowling on Schooners.
We believe it to be lignonvitae wood, as it is very dense and heavy . The iron lines holes do not go all the way through, not a part of the rigging, finger holes! 8" diameter