This is a Georgian gentleman’s treen library & gallery magnifying glass with a turned handle and a lovely reeded  circular frame. There are brass fixing attachments where the handle attaches to the frame.  This type of magnifying glass was used to inspect paintings amongst other things and is often referred to as a viewing glass. It has at some stage had the glass replaced, many examples do  and is in working order.
It measures 33cm l x 16cm w x 2cm d.