Here is a link to Kirby Ross's info about G.O. 3 companies:

http://www.civilwarstlouis.com/militia/federalmilitia.htm#7.%20Missouri%20Militia

The St. Louis County Public Library Systems also has info about these and other types of militia companies.

http://www.slpl.lib.mo.us/libsrc/mocivilwar.htm

My great-grandfather belonged to a G.O. 3 company in Bollinger County. I think the "V" stands for Volunteer.

George Williams