filters for black and white film
Someone had these old Ricoh-filters with a diameter of 43 mm which fits my Cosina Voigtländer 40 mm og 75 mm lenses. I think they are ment for the Ricoh rangefinders, like Ricoh 500. I haven't taken any black and white photos with them yet.
schneideroptics (B+W) has some more info on using filters for black and white photo at «Filters for black and white film»