I've used the Rollei duto inthe past. Unfortunately it would take an extraordinary effort to find and example and scan it. I tend to like results from duto better than most other soft filters
I have a permanently softened Rollei. It has a fingerprint etched into the taking lens, the result of a previous owner getting careless (in his old age) after working with mild acid and handling the camera. It makes for interesting images, but not always what you want. I sort of like the idea of having the choice.;>)
I have the Rolleisoft 0 and 1 filters for both bayonet 1 and 2, and the earlier Duto-filters for the Rolleiflex Standard. They are all of the Duto-type with concentric rings that superimposes a weak unfocused image onto the focused image, creating a nice softening effect. The effect is depending on the aperture, and it's not recommended to stop down more than max f:8.
I haven't used them much. but here's an example taken with the Rolleisoft 0: