On the opposite valve cover, passenger side, do you have a tube that empties to the ground or do you have a hose that comes out of the valve cover and attaches to the back of the carburator spacer? If you have a down draft tube (black tube that points down to the ground) then it is an open, if on the other hand you have a tube running to the carb then it is a closed.
The open type simply has vent holes in the base of the breather cap whereas the closed type has no vent holes, rather a hose nipple on the side. The open type is simply installed on the valve cover. The closed type has a hose going from the nipple to the air cleaner. The position on the air cleaner is inside the perimeter of the air filter.
If you need the closed type, there'll be a hole in the air cleaner or a small fitting on the bottom for the hose. If you have an aftermarket air cleaner, it may or may not have the nipple (or fitting) attached. If it was installed incorrectly when purchased, it may have a punch out for the plastic fitting that's never been used.
Open breathers are likely acceptable for cars in most states. Some states like California that have inspection systems may want you to install the closed type system in order to pass the state vehicle inspection.