Cocktail shakers can come in a wide variety of shapes, sizes, and designs. One of the earliest versions is what is known as the "Boston Shaker". It consists of essentially a "2 part" shaker, with two vessels of slightly different size, such that one vessel will fit snuggly within the other. At least one of the vessels (the larger one) will almost always be made of metal, the other will be made of either metal or glass. If glass, it will be what is typically known as a "Pint Glass".
It is believed that this type of shaker was in use by the mid 1800 (need citation/evidence).
The respective sizes of the two different parts of a Boston Shaker can vary slightly, usually the larger tin is 28 ounces, with the smaller tin/glass being 16 ounces.
When the second part used is glass, while it might be the same "size" as a simple pint glass that beer might be served it, it should be made of better quality glass in order to prevent chipping and breaking.
When the second part used is metal instead of glass, it is sometimes referred to as a "cheaters tin". It can vary in size, but usually either 16 or 18 ounces. Since the metal tin will have thinner walls than glass, a 16 ounce tin will fit deeper into the 28 ounce tin, this is why most people use an 18 ounce tin instead.
The simplicity of this type of shaker/mixer almost defies identifying when it might have originally come onto the scene. It would be relatively straight-forward for a bartender to simply utilize what they already had on hand. It is believed that the notion of simply pouring the drinks ingredients and ice back and forth between two vessels was one of the earlier forms of mixing up a drink (that, and simply stirring it). It wouldn't take that much ingenuity to notice that the two vessels could be held together and shaken to do pretty much the same thing. This is also illustrated by one of the earliest known patents for a "boston-ish" mixing device from 1866, in which the form of the two part Boston Shaker is clearly evident, but with an "improvement" added in order to facilitate straining.
|Patent: Improved Punch-Mixer and Egg-Beater 
By: Thomas Fisler
Dated: April 17, 1866
- The History of the Boston Tin Cocktail Shaker (Beaumont Limited)