This machine is named after a Swedish maker and dealer, "Michael Wallmo". Like MK-1 "Hart" machines, MK-2 "Wallmo" was developed about twenty years ago. Though this machine comes with a screw and washer, should you not want them showing you don't have to have them as like the "Hart" machine the cog is shaped in such a way that the very action of placing the worm and thumb screw on will hold the cog in place. As you can also see from one of the pictures this cog can also be used for five string conversions. The bass that is pictured is and English instrument made by "Mark Dearlove", and has had these machines on for at least the last twenty years. They still work well and will out live us all. Again, very low geared for fine tuning.