Nesting screwdriver set

[Sudsy]

Nice little brass no name set
Each one fits inside the one above

[Sudsy]

Oops just noticed I cut off the markings on the ruler editing the photo to fit here, but if you count em it's 6" (just under)

[Plyerman]

I've had a few of those sets pass through my hands over the years. Some versions have a small hammer as the main part, with the screwdrivers nesting in the handle.

[mvwcnews]

The concept has been around for quite a while.  I thought I remembered an ad, & a quick google / books search turned up a 1918 description -- I condensed the pertinent parts into a single image.  E. Edelman produced a wide range of hardware specialties.