[Y-Blockhead]

Originally Posted by rotorwrench

They set them for right and left but is hard to tell whether you have a right or a left on an old model A unless you take them apart and see where the valving was set. They could tell back then by the way the arms were installed. Now days you don't know on and old crusty antique.

It should be relatively easy to tell since the arms only go on one way, shouldn't it?