Product Description
Here is a small, but essential part of an ignition system.
This vacuum can is necessary for engine timing. It is part of the total timing, where the distributor is adjusted fore-aft to advance or retard timing.
This can gets its vacuum from a tube that normally runs to a port on the front of the carburetor.
Here is a photo of the real thing along with it on an HEI distributor.

This fits over a 1/16" diameter shaft but the can could be cut off and glued at the very bottom of the distributor cap.
It is normally aluminum, so paint it accordingly. This can be used for a distributor of any number of cylinders.
One vacuum advance timing can, by Greg's Scale Model Accessories, 1/25 scale.