This sale is for an excellent condition Mamiya C Waist Level Finder for C series cameras. It certainly fits the C220 and C330 cameras; I do not have any earlier models to test it with.
This WLF is in great condition. There are only normal very minor signs of use. It is fitted with the standard -1.5 dioptre.
This is an really sought after item – not easy to find. Just try finding another one (apart from in Japan at crazy prices, plus shipping, plus import duty, plus dodgy Japanese descriptions. Good luck with that!).