You most likely have the remains a AC Spark Plug retrofit kit. The state of California required a closed PCV retrofit on all light vehicles from 1950 through 1960. Starting in 1961 all California cars and light trucks were factory equipped with closed PCV system by law.
An AC Spark Plug retrofit kit consisted of freeze plug to seal the crankcase after the draft tube was removed. Hose barbs and a hose were installed from the air cleaner to valve cover (provides clean air to the engine). The vented oil cap was removed a replaced with sealed oil cap. Another hose barb was installed in the side of valve cover towards the front of the engine. A quarter inch hose was attached to the barb, the other end of the hose is where PVC valve was installed. The other end PCV valve connects to 3/8" hose. This hose was then connected to brass block installed on the intake manifold.
The AC part numbers were CV3 for PCV valve kit. The state of California required the system be closed, so another kit (KV1002) was required to seal up the engine, it contained a sealed oil cap, freeze plug for road draft tube, and a hose kit from the air cleaner to the engine.
The PCV valve in the CV3 kit was CV609. Is this the "filter" you are talking about? CV609 valves are easy to find on Ebay.
It rare to find a complete kit on these engines, most were "modified" somewhere down the line. Most people did not understand system and removed/modified it.
