Housing only 1" diameter, it's threaded shaft is 3/4" diameter and also 3/4" in length to allow for fitment to thicker dash panels, fiberglass or wood as well as steel. There is also 2 flat sides to help prevent the switch 'turning' in the panel as it is being used. 

This Universal 12V Keyed Ignition Switch has a Anodized Black Aluminum Art Deco Style Bezel.
Key turns clockwise for 'Ignition' and then 'Crank'. Key position can turn anti-clockwise one position (From Off) which is 'Accessory'.

Other dash switches with matching Art Deco Knobs / Bezels are available on our other Ebay listings.