It is made of slightly satin white metal, perhaps a very low-grade silver alloy. The acid test is negative.
I have not managed to identify the families corresponding to these coats of arms under a marquis' crown and framed by two laurel palms.
The engraving is well detailed, with the irregularity specific to old engravings.
The grip is structured, in a way typical of 18th century thumb seals.
3.4 cm high
2.4 x 2 cm for the matrix alone
14.42 grams
Very good condition.
Hand delivery in Paris or insured Colissimo shipping.
France: €15
Europe: €20
World: €35