One of Sekonic's earliest meters, and the first of the "Leader" line. This one has a hinged door on front, similar to the General Electric DW series, except it's spring-loaded and all you have to do is push the little rod on the right side to release it. You compensate for it by using the "open" and "closed" marks on the dial.

So what you do is you set the calculator to film speed, then read off the number on the meter scale. You take that number on the outer dial and turn it until that number is next to the "open" or "closed" pointer (depending on the state of the door), and read off your pairs. Or, if you simply take your film speed as being the shutter speed, you can direct-read the ƒ-stop right off the meter face.

Nothing earth-shattering here, but it's a nice little meter and a taste of what was to come in later years.