What does I S mean?

I have a few forks marked (eagle) Wm Rogers (star) and then the capital letters I S
There are no other numbers or mrks of any kind.
Is this sterling or not?

Enasteri

The Rogers marks are confusing to say the least as there were a large number of Rogers makers and companies. The mark you describe is a silver plate mark that was used until about 1976. Post a picture of the mark so we can be sure - the size of the letters in “Wm” is important.

Regards,

Uncle Vic