could anyone explain how the adjustments on a voigtlander scopar b scope work the scope looks like many ive seen on war sniper rifles there is a turret on top marked 100,200,300yds with a stem pointing toward rear on the tube it has minus 3 to pluse 3 in graduation marks and looks like eye piece could rotate scope is numbered to the rifle was completed in 1908 I would like to use it but would like an idea on how too operate controls without experimenting turning things thank you