17thc Silver Cased Knife & Fork

A rare silver knife and fork set housed a superb contemporary shagreen case , the steel knife blade has a makers mark stamped on it , the fork is unusual as it has four tines instead of the normal three this is solid silver although not hall marked the handles have nicely shaped terminals similar to the fancy shirt cuffs and collars of the mid 1600s also in silver, we are not sure what the handles are made of it is similar to red amber or agate ? (Perhaps someone could shed some light on this for us ). This very handsome rare item was made in France in the mid seventeenth century & is in superb untouched condition with some rusting on the steel blade  . ( sizes are approximate).