Special Tool for tuning the Stromberg 175 CD carburetors.
Please note that this is the version with the "Allen key" end.
It locates into the piston assembly and allows you to rotate it.
Turning it clockwise raises the needle and enrichens the mixture; turning it counter-clockwise lowers it and consequently weakens the mixture.
Throughout the years, Stromberg (and consequently Zenith which are similar but in name) has used various ways of adjusting the mixture.
This version here uses the hexagonal head that you might also recognize as an "Allen key".
The other version is dubbed "raised blade" or "Slotted Head" by Stromberg but is basically a slotted head.
This latter version can be found HERE.
Either version is a vital tool for both the DIY mechanic as well as professionals!
Also fits similar versions of the Stromberg 125 CD and Stromberg 150 CD.