I am trying to track down the date range and reference for the following
Illinois Glass Co. maker's mark: "IG Co" inside an elongated diamond
embossed on the base of the bottle. The bottle in question comes from a late
19th century California gold rush site. I've searched what bottle reference
books I could get access to, such as Toulouse, Wilson, and Polak, and the
only mark I came across was the standard "I" inside a elongated diamond. If
any one is aware of the mark in question, please let me know.