This is a fascinating late 19th or early 20th century miliner's tool

It is made of two pieces of turned & shaped dark red-brown coloured wood.
A thick double ended screw connects the two halves, and they can be moved by twisting the handle at the front. There is a guide bar near the base to stop the pieces twisting

This was a working tool, there are some scars on the wood, and the handle has a dark patina. It still works well and the mechanism turns smoothly.

Dimensions : Height 11" (28cm), Width 6¾" (17cm), Depth including handle 12" (30.5cm) 
Weight : 4.2kg (9lb 4oz)

Ref : Hatstretcher012