There are 3 Brands of Sock Machines that you will find the most, they are the Legare both a 47 and a 400,  the Auto Knitter, and a Gearhart. 

Legare

There are 2 Legare machines  a 47 and a 400,  it is thought that when these machines were being produced that the Legare 400 was the top of the line.  Both machines are a very well built machine.  The cylinders that are found most with these two machines are the 54 slot and a 72 slot.  The machine may also have a ribber with it, the ribber will have 36 slots. 

The cam shell or the path that the needles travel is a bit different on the Legare 47 vs. the Legare 400.

Auto Knitter

The Auto Knitter machines are very nice machines, and tend to be a very smooth machine to use.   The cylinders that are found most with the Auto Knitter are a 60 slot and a 80 slot.  The ribber dials come in 2 sizes a 30 slot and a 40 slot.  There is also a Canada Auto Knitter that can be found with a 72 slot cylinder and a 36 slot ribber.

Gearhart

The Gearhart machines are also a very well made machine.  The can have a wide range of cylinders and ribbers.   They make a very nice little clicking noise as the needles run over the uplift cam, it always reminds me of the playing card in the spoke of the bicycle tire when I was a child.

The Gearhart machines do have one difference in that the gear handle when cranked does not equal one time around the cylinder as in the Legare or Auto Knitter.  This does take a little getting used to.  A Gearhart machine does not have the ability to take the ribber out of action to enable you to do ribbing down the top of the foot.