I used a small hand trowel today to probe into the root bulb. Every time I heard it hit glass, I'd dig around it until I could pry it loose with my fingers.
also, the Pabst Milwaukee bottle I found is strange. The seam stops under the lip on one side and the glass is about 3 times thicker on about 1/4 of the bottle near the bottom. It is a brown bottle and it looks as though there are a few yellow bubbles in it.