Take a good look at the pictures below. This is what you usually see inside the intake air scoop when you remove the chrome grill. I think a lot of owners don't even know. There is a screen in there. The original screen is not very robust, and it does not really filter the air. It just keeps out junk. We only have a few genuine right-side screens left, and once they're gone, there will be no more. But Kent has developed a new cabin air filter that will actually filter the air, not just attempt to keep out leaves and needles. Check out his kit below.
Product Details
This is what a genuine filter screen looks like installed
This is what the upgraded cabin air filters from Kent's kit will look like when installed. Note they totally seal from any outside air leaks, unlike the genuine screen pictured above.
Related Products:
Restoring a W108 ro W109 Cabin Intake Air Vent Assembly - On Demand Video
In this xx-minute instructional video, Kent will cover grill and vent cover removal, inspection, surface rust repair, filter replacement options, other items to check and do, and reassembly of all components. If you are interested in having true "cabin air filters," see his kit below.
1965 to 1973 W108 W109 Intake Air Screen to Air Filter Upgrade
This will actually give you true cabin air filters. No just screen! This is an easy DIY kit that will require you to cut the filter material from the patterns included and lightly glue it in place with the glue supplied.