Pacific

Wow. I can hear the waves and feel the wind. Aren't those old Zeiss folders wonderful?

Yup, I never thought I would like scame focus folders, but this Zeiss Nettar is such a joy to use. Now if I can only figure out how to put filters...

Oh, that's easy-peasy. They use "series" filters. The actual filter sits in a circular adaptor ring that pressure fits onto the lens. The adaptor has a circular flange that you push into a slot around the glass on the lens. They come in various sizes designated sometimes by Roman numerals. I think yours would use a 6 or VI. Here's a pretty decent article. http://silverbased.org/series-filters/ They are cheap and not too hard to find at swap meets or used camera stores. Since you're in San Diego, I would bet that Camera Exposure on Adams Ave. will have them.