Hi, My name is ***** ***** it is my pleasure to assist you. The I S stands for International Silver Co.. Yes your first serving plate pattern Joanne from Wilcox International Silver Co. the value in good condition $55.00 to excellent condition $75.00. Your second serving plate pattern Brandon Hall from Wilcox International Silver Co. the value in good condition $45.00 to excellent condition $70.00. I hope this helps you. Thanks Mike
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