I used a slightly damp Scotch-Brite scrub sponge and gently (that means not very hard) scrubbed the bakelite parts that are real dirty. I've also just used a cotton ball and some denatured alcohol. Be careful with the metal name plate as you can scrub the paint off. I had one with a sticky shutter and put a little "3 in one" oil on it, worked it a few times and then soaked it in denatured alcohol. Works like a charm. I've cleaned four of them with great success. I warning, don't drop them as bakelite doesn't bounce. I had one in a padded case that I dropped and it was toast. If you plan to reverse the lens, just remember how it came apart. Bill Barber