I wear one just like it most of the time when working with the machines. Keeps the oil off of my clothing and the chips out of my pockets. It also has the swinging micrometer pocket, a nice feature.
Just out of high school (about 3/4 of the way through the last century) I worked in a machine shop for a year. I could choose between an apron or a lab coat type of smock with half sleeves. Most guys wore the smocks because they did a better job of keeping oil off of your shirt than an apron did. Additionally, the smocks were long enough to cover your pockets, but were not as long as an apron. If I could find a smock like that for here at home I would probably wear one of them.