I have both types, the camless one requires adjustment of width and length and a bit of testsewing, and it's very good at what it does. I have the black version in the picture, the later with the "nose" behind the needle, the earlier are exactly the same but with out this tiny detail. Can be adjusted for any size within it's minimum to maximum range.
The versions with cams are very easy, no adjustments at all. Choose the cam size you need, any adjustment is related to tension and maching neede size and thread weight. This reminds me, I need to sort out the cams for mine, I need the extra set, and I need to confirm I get the right ones. I suspect there has been a mixup with mine.
The price isn't way off on this buttonholer, it's in good condtion box and all, complete with manual and fitting screws. Mine is missing the manual, and I guess I will have to pay a few pounds to get it, and even more to get the additional cam set.