The "G" in the 211G156 means the machine was manufactured in Germany. It is, coincidentally, also the type of bobbin that the machine uses, which is approximately 3/4" in diameter. This is not considered a large bobbin. An "M" bobbin is about 1" in diameter, and a "U" bobbin is a little over 1 1/8" in diameter. Those are considered large bobbins, but your machine can only use a "G" bobbin. BTW, the "L" bobbin is used in home sewing machines.
That machine looks like it is in great condition, how much do they want for it?
Here is the link to the service manual for the machine: CLICK HERE