Kodak Self Timer, allowing the user to make "selfies" long before the term was adopted in our modern era. Although such things might have been regarded as narcissistic in the 1920s, as the instructions only suggest it might be used to insert oneself into a group. It has been found in a Kodak catalogue from 1918, so this is the date allocated. The timer is used with a cable release clipped into the top. The device is restrained by a partial vacuum, after triggering the timer a robust spring sets off, the initial travel is quick, but this rapidly forms a vacuum behind the piston it drives. Air now leaks past a hard rubber seal slowly allowing the piston to travel, the time being determined firstly by the adjustable screw in the base of the timer and secondly by drag in the cable and shutter combination. Towards the end of the piston travel a hole is uncovered, this allows the chamber to rapidly fill with air releasing the spring and firing the shutter. The spring is quite strong, so don't be tempted to take one apart, it's tricky to get back together. It's not a good idea to use these timers with the old linen covered cable releases, as the linen won't be up to the task of holding the pressure from the spring and will most likely snap after a couple of uses. Far better to use one of Kodak's later metal covered release cables. Although technically from a later period, they are up to the task. Kodak models are best as Kodak used an elliptical section for the plunger head and the timer is shaped accordingly. The metal ones are a little thicker in this respect, but they still fit reasonably well. Below is a Kodak No.5 metal cable release.

This Kodak Self Timer was added to the collection in November 2019.