An early 1800's rigger's serving mallet used to wrap marline around a splice in a rope.. The groove in the head fits around the splice and a turn of malice is taken around the handle, friction holds it tight. The tool is then rotated around the rope.

This one measures 16.5cm l x 6cm w at the widest point x 1.6cm d 



For more info on antique treen sailmakers tools  see link below’s-Liners

Antique Treen Rigger's Serving Mallet