CH 1937 210x Automobile Post Office I FDC on matching picture post card

Switzerland 1937 special stamp for the automobile post offices (issue I, 3 lines between the mountain peak and the edge),
Fiber mix black and red (210x),
single value FDC on matching picture post card with Saurer Automobil-Postbureau,
cancelled "5.IX.37 - 1. Schweiz. Automobil-Postbureau", and red Postmark "Jahrhundertfeier SIA BERN-GURNIGEL", good condition,
Catalog: SBK 210x, Michel 311x.