[Huib Ottens]

Hi Theodor,

Thanks for the scans. I was referring your Dreieckrechner, but the other scan is also welcome. I was hoping for a Dreieckrechner of Bulgarian origin. Dreieckrechner of Hungarian, Swiss and British origin are known to exist.

I think these Dreieckrechner are highly collectable items. There are many versions of this instrument, and Siegfried Knemeyer himself is also a very interesting subject.

My personal collection holds 18 (14 versions) Dreieckrechner at the moment.