Parts of a manometer There is a poor quality photo in the diagram of a manometer below:



The picture is too poor for me to understand what they mean by "glass pointer marks calibrated volume".  I would be interested if anyone (a) knows what this is - preferably with a manufacturer's number so I can inquire further or (b) has a higher quality image of the part.
I can't tell you a manufacturer, but I can tell you the purpose of the pointer.

When the height of the column of mercury changes, it changes the height of the mercury exposed to the atmosphere. Since the ruler is (usually) fixed in place, the level of the mercury needs to be adjusted to the zero on the ruler. The pointer shows you the zero point. You adjust the level of mercury so that it barely touches the point.