I cannot teach anybody anything; I can only make them think.
Socrates
Around 1877 the Swedish public school teacher Per (Peter) Johann Bäckman from Stockholm invented an adding device, similar to the earlier calculator of Charles Henry Webb, and applied for patents in Sweden and Germany. The Swedish patent №205 of å framstäld räknemaskin för addition for nine years was granted on 11 April 1878. German patent №2615 for Rechenapparat für Addition was granted on 28 March 1878 (see the German patent of Bäckman).
The adding device of Bäckman was put in production, although on small scale, between 1885 and 1890. The price was SEK 10 (or 15 SEK), but due to low demand, production was soon discontinued and the workers each received a copy as a gift.
The dimensions of the black metal adding device of Peter Bäckman are as follows: height 30.0 mm; length 172.0 mm; width 100.0 mm. The weight is 2.5 kg.
The machine was advertised in several Swedish newspapers, for example, see the nearby advertisement from the 29 December 1878 issue of Dagens Nyheter newspaper:
Machine Agency
KARLSTAD
A fitting Christmas present.
P. JOH. BACKMANS
patented
Calculating machine for addition, and speed calculations, simple and easy to operate, particularly suitable as a controller when measuring and weighing all kinds of goods, loading, and unloading, and a good helper for bookkeepers. Now in stock and sent by cash on delivery or by post.
J. W. NORDQVIST
Price 15 krones.
Biography of Peter Backman
Peter (AKA Per) Johann Bäckman, born 11 June 1850, and died 12 April 1904, was a schoolteacher, rector, author, and one of the early leaders within the Swedish Good Templar movement.
Bäckman was the founder and first rector (from 1878 until 1889) of Kristinehamns Praktiska Skola, which started its operations in 1878. Per Johan Bäckman introduced co-education for both sexes in 1880 and the teaching was conducted in two rented rooms in Kristinehamn. After retiring from the Praktiska Skola, Bäckman became a director of an insurance company.
Bäckman wrote a practical textbook in the Swedish language along with spelling and foreign words with explanations.