explaination for these three dots on bottom

[kranked003]

hi
posting a pic of bottle bottom. whats up with these three dots? its clear glass and has a long bubble in neck and sadly cracked in neck too.
thanks
E

 

[kranked003]

heres the top[]

 

[CanYaDigIt]

I'd say the spots on the base are probably mold vent marks. Just a guess.