I just submitted an article about the Interstate Glass Company of Kansas City, Missouri to glassbottlemarks.com describing the history of that company. It was in business for 18 months from 1901 to 1903. The mark is ISGCo. The bottles I have have it on the base. It could also be on the heel. It may be on insulators or fruit jars. If you have any bottle with the ISGCo logo on it could you let me know please. Right now I know of eight different bottles with embossing and one amber slick beer.Thanks for your help. Scott