This helmet is an aluminum, Swiss, "Civil Defense Helmet", Model 1918/46, also known as the M18/46 helmet. Model 1918 refers to the original helmet shell style designed in 1918, and the 46 refers to 1946, the first year of issue for the Aluminum shells that were made for the National Civil Defense Forces.
These aluminum helmets were first made in 1946, in response to feedback from firefighters and civil defense responders in the field. Their complaint about the steel military version was the weight. The weight problem was solved by choosing a lightweight and very strong aluminum alloy know as Duralumin. You can read more about this alloy here:
The majority of these M18/46 helmets were painted yellow, some completely, and some with just the exterior painted. Yellow was the official "National Civil Defense" color. Some of these helmets that were put into service with full time fire departments, were painted other colors like black or red.
The liner in my particular helmet is the late style, that was instituted sometime in the 1960's.
The three pads are riveted directly to the Darlumin shell. The outer layer of the pads is a synthetic "leather", with a removable fiber pad inside. This is a very distinct departure from the steel helmet liners that had pads attached to a metal band.
The strap connector is a basic wire hook and loop type design.
All in all these look like they would make very effective, lightweight field helmets. Even though the liner is a basic 3-pad style, they are quite comfortable and secure to wear.
These M18/46 helmets were used into the 1970's, until the new synthetic, modern, fire and rescue helmets were issued. There are no dates or makers marks on my helmet, but the synthetic style liner pads date this helmet in the the 1960's to 1970's time frame.
There were also a very small number of M18/46 helmets made out of plastic for use in electrical environments, but these are very rare and seldom encountered.
As an interesting comparison, you can check out my previous blog posting on my WW2 vintage, M18/43 Swiss military helmet.
And now to finish things up, here's the photo album of this wonderful Swiss helmet.