SIEBER was located in the small Swiss Italian town of Chiasso. This company was also famous for it's handmade tubular ("sew-up") tires and  aluminum and maple wood rims. Bicycles, crank sets, brakes, shoes, and hubs were among the products sold under the prestigious Sieber label. Please see the interesting Jobst Brandt article about his visit to Sieber in 1959 in the Trento Bike pages. It is apparent from this report that the production of tires and bikes had likely ceased by that time.
     Sieber bicycles were very refined, with extensive shaping of the lugs and delicate pin striping... Obviously a "high line" of products.