CH 1937 210x Automobile Post Office I FDC with address

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),
FDC white cover with address, cancelled 5.IX.37 "1. Schweiz. Automobil-Postbureau", and red Postmark "Jahrhundertfeier SIA BERN-GURNIGEL", in good condition
Catalog SBK 210x, Michel 311x.