Cobalt blue bottle with decoration - M in circle on base
I'm looking for information on this cobalt bottle. On the bottom there is an M inside a circle. The number 2 appears about 3/4 of an inch below the M. The bottle itself is 8 inches tall by 3 1/2 inches wide. 
Comments
I have seen this bottle but cannot recall whether it is a Magnesia bottle like Philip's or not.
The M in the circle is the mark of Maryland Glass Company of Baltimore, MD. This mark was used after 1916.
Your bottle is likely mid 20th century.