It's made by Owens Glass Company. The left number is usually the plant number, so 7 is Alton, IL. The right number is the year number (usually only the last digit of the year, since the diamond logo was not used till 1929, it could be either 34, 44 or 54), and the bottom number is mold number. They used the diamond logo from 1929-1954. Here's the page where you can read about them more: SHA Owens-Illinois Glass Company