I can tell you from years of experience, the "Jim" letter will not be a factor here. It just kinda is what it is. A good start would be to keep looking for a photo match, or at least a style match that shows these stenciled white numerals were ever worn on Milwaukee helmets.

You can return the helmet if you're not comfortable (Ebay does allow you to, regardless of what the seller says), but you'll have to do it in a reasonable timeframe.