Addendum: 4 1/2" x 3 1/2" - that's probably 9x12cm. So the lens is probably a 135mm or 150mm. I don't have my library with me, so I don't know what kind of lens the Ernemann "Doppel-Objektiv Serie A" is, but I know I can find out.

The holder looks like it might be "Normalfalz", but it could be some other type.

I would guess at early 1920's for this camera, and for some reason the shutter looks to me like it could be a Koilos. "O" is "Offen", or "B"; "Z" is "Zeit", or "T"...