The frame is made from 18ct white gold and the clips from platinum and diamonds

The frame is marked PLAT & 18.

The diamonds are collet set . The largest are 5mm across ( 2 number)

The next are 3.5 mm ( about a dozen )

Then are a group of flat set pave style diamonds surrounding the main two . These fill all the space in the S shape in the centre and range between 4 and 2mm.

There are a few tiny ones as well and also polished discs of platinum about 2mm across which are very reflective. 

They are all extremely ice cool diamonds 

The Queen had a few ( though her diamonds may be even better - I'm never allowed that close )

The brooch unassembles to form two identical dress clips which can be worn in a variety of ways.

Maximum dimension 2.5 inch 

Width averages 2 inch 

Height averages about 1.1 inch

Weight 17.6 gms

Come in an old box which is probably original