SIlver plate 1793.?

Kind regards from Zagreb, Croatia.
I have the big plate (I suppose silver with something). Please could You help me with some information about it. Thanks! In addition are photos.

Your plate is probably pewter. If you search the internet for ‘“s duncumb” pewter’ you will find several hits including one which describes an item for sale at auction as ‘An 18th century pewter charger, with touch marks ‘S. Duncumb’, a crown over a Tudor rose and a ‘London’ banner’ which sounds very like what you have.

Yes you have right. Really you helped me very much. Big thanks to You.
Kind regards from Zagreb and Croatia. Drazen