The middle picture shows an open pontil on the base of a cylindrical medicine bottle.
The third picture shows the base of a milk bottle from just after the trun of the century.
I have put up pictures of the lips so that the readers can see how they mold goes all the way over the top as shown below. This is different than an older hand tooled, hand blown bottle.
With the uniformity, came the possibility to create a solid seal with a screw cap.
the bottle on the right appears to have a tapered collar a form which was very popular for more than 60 prior to the making of this bottle.
This is the base of the bottle whose lip is shown above left.
The food and household product industries on the other hand widely adopted the screw cap quickly.
One unique closure to the late 1930s was a three point screw top.