General Information: Collectors sometimes refer to the Spanish Model 1926 helmet as the “con ala” helmet which means “with wings” in Spanish. This is to distinguish it from the earlier, low-production, Model 1921 which had vertical rather than flared sides like the M26. The M21s are also known as the “sin ala” version. The M26 closely followed the design of the German helmets of the First World War with their skirt sections providing protection to the side and back and the raised visor. The liners also resembled the German WWI models with their sets of three leather pads with two tongues on each and perforations to accommodate a liner string. The pre-Civil War versions of the helmets had hollow rivets. The M26s were originally painted grey, although most were repainted during or after the Civil War, typically in brown or green.
The helmets were developed by the National Arsenal of Artillery at Trubia in 1926 (see also Spanish M38) and were officially adopted in mid-1930 at which time an initial order for 20,000 helmets was placed. The Spanish M26 was used throughout the Civil War by both sides of the conflict. Starting in 1943, along with other types of helmets in service at that time, a metal loop was soldered on to the front of the helmets to accommodate a brass Spanish army badge. 
Displayed Example: I got this from an Australian collector friend. Post-Civil War modified versions of this helmet abound, but it is really difficult to find one with its original grey paint, pre-war hollow side rivets and intact original liner and chinstrap. One of the liner pads on this specimen has come loose from the liner band, but otherwise it is all there and all in its original factory condition. I was very happy to add this one to my shelf.
This helmet replaced one that I purchased in Spain in 1972. I was thirteen at the time and accompanying my father who was traveling to Spain on a business trip. Dad gave me $15 (a big amount of dough for a thirteen-year-old at that time), and set me loose in the famous Rastro flea market in Madrid while he attended a business meeting. Armed with a very rudimentary knowledge of Spanish, $15 worth of pesetas, and a big dose of eagerness, I set out on my adventure. The Rastro at that time was a very cool place for a thirteen-year-old boy with an interest in history and military relics. There were several dealers at the Rastro who specialized in relics from the Civil War. I remember rifling through boxes of ground dug pistols, bayonets, belt buckles, rusty helmets of various types, and the like. Eventually I found a near mint condition, post-Civil War refurbished (although I did not know that at the time), M26 with bracket soldered on the front for an army badge. Elsewhere I found a badge to attach to the front.
Collector Notes: The M26 can be a relatively inexpensive addition to a collection. If you are aiming to acquire one in that was not post-war modified, this is achievable for the patient collector and the market does not distinguish war-time and post-war versions of the M26 in terms of valuation, so they can be purchased without breaking the piggy bank. One thing to watch out for are examples that have communist or anarchist acronyms or symbols like the one in the period photo on my home page. The ones like this that you see on platforms like eBay are almost always fakes.
 Marzetti, 2003, pp352-357