Exceptionally rare, authentic 1910s French OLEO 75 finned all-brass spark plug. This early high-performance plug features highly distinct, machined cooling rings (fins) designed to dissipate extreme heat. Plugs of this specific finned architecture were utilized on early aviation rotary engines (such as WWI-era Gnome-Rhône or Le Rhône engines) as well as premier pre-war French racing motorcycles and cyclecars (Peugeot, Alcyon, René Gillet).

  • Solid Brass Body: Features the highly sought-after, early-production all-brass hex shell shell with beautifully preserved cooling fins.
  • Mica Core: Equipped with its original, robust, dark compressed mica washer insulator core—engineered to withstand the high vibration and thermal shock of early open-crankcase motors.
  • Crisp Historic Stamping: Explicitly stamped on the brass hex flats with "OLEO 75" and the historical French patent mark "BREVETÉ S.G.D.G." (Sans Garantie Du Gouvernement).
  • Thread/Base: Features the early tapered pipe thread / adapter configuration with a fine knurled accent ring. Threads are fully intact and clear of modern stripping.