1913. Not issued: 50 C. Airmail Olten Oensingen, cut, unused with original gum with trace of hinge and affixed spot, issued only 32 examples, hardly once offered Switzerland and airmail issues rarity, expertized Hunziker and photo expertize Jean Claude Marchand SBPV (2023) \"rare stamp\", Michel 8.000.- (Zumstein no. OI)