Welcome to Just Answer and thanks for your question. Old Ivory was the back stamp used by Syracuse from 1946 to 1960. It isn't the name of the pattern. Are there any other markings that might help identify which pattern it is?
That is the manufacturer's mark. Syracuse/O. P. Co. is the same thing. Here is a link to a site that sells replacements for china patterns. As you can see, there are dozens of patterns. Perhaps you can find the one that is yours from among them.
Sometimes similar patterns would have names like Colony - Red, Colony - Blue, Colony - Green. Did the one you saw on Ebay have a name? The link I sent you contains pictures of almost all of the patterns that Syracuse ever made. Can you post a picture of a plate and I will try to find it for you. You use the little tree icon (between the smiley face and the you tube icon at the top of the reply box.