Full Details

Name and Model Number Billeter National
Rechenwalze System 20-m
Country of Origin Switzerland
Date of Manufacture c. 1920
Front Scales Cylindrical C & D scales in 80 sections
Back Scales None
Scale Length 20-m
Type of Rule Cylinder
Construction Varnished paper scales on metal cylinder (20.5-cm dia. x 57-cm long) & on sliding cylindrical cage. Metal support stand.
Area of Use Financial
Comment Formerly Julius Billeter Rechenwalze. This cylindrical slide rule has a metal support stand that could be wall mounted. Commonly used by European banks for currency trading. This is a previously unknown size. The largest previously known National cylindrical slide rule had a 16-m scale length.
Rarity RRR
Donor Collection of Ed Chamberlain
Match Number 154
(Click Picture for Details)

In conjunction with our 'donors' we assign a rarity rating to each item, based on the system devised by Herman van Herwijnen
(1929 - 2004), renowned Dutch collector, author, and creator of Herman's Archive, a collection of 5,000 slide rule images on CD.
• RR = Rare - 1 of 25 collectors has one; it may take a year to find an example in the marketplace.
• RRR = Very Rare - only a few known to collectors; may be several years before it comes up for sale.
• RRRR = Extremely Rare - a museum piece; unlikely that an example will come up for sale.