I learned to use the Dalton MK4A in 1967, I still have it, as well as a MK5A the mini version. I have found it very useful for the past 43 years and have always carried it in my bag. As well as the usual high and low speed slides it has been used with CARP and MEARS Slides, which I doubt anyone has heard of. I like to think of it as a Prayer Wheel that comes in, in times of Desperation.