Double-stamped base

[chosi]

I recently bought a blown crown top bottle, and I noticed that the embossing on the base (bottom) of the bottle was "double stamped". That is, the embossing shows up twice, once strongly and once weakly at about a 30 degree angle. But the embossing on the rest of the bottle is normal.

Can anyone explain to me how this might have happened? I thought I had a pretty good idea how blown-in-the-mold bottles were made, but I don't understand how the bottom of the bottle could have this ghost embossing at an angle while the embossing on the rest of the bottle looks perfectly normal.

 

[KentOhio]

Before the bottle was fully blown, that part of the glass dripped down and settled in the mold, picking up an impression. When the blower gave another puff, it shifted the glass slightly and made the newer, crisper impression.