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For slide adders there is no doubt that Germany was the major manufacturing country during the middle of the twentieth century and more models originate from there than the rest of the world put together. Otto Meuter was, like Addiator and Addimult, a major manufacturer with a range of models.
“The Pocket Adding Machine”
Believed made by Otto Meuter (Sterling version of the Pro Calculo)
8 slides, 9 digit display
Aluminium & steel
4.8 x 3 inches
With imitation crocodile skin case, stylus, and instructions
1920s
Produx Original (Otto Meuter &Sohn, West Germany)
8 slides, 9 digit display
Aluminium & steel
6.5 x 3.4 inches
With green/clear PVC case, stylus and instructions
1960s
Obtained from USA
Produx Original (Otto Meuter & Sohn, West Germany)
Sterling currency version
8 slides, 9 digit display
Aluminium & steel
6.5 x 3.4 inches
With green/clear PVC case, stylus and instructions
1960s
Identical to the decimal version except for the front face and slides, indicating how easy it was to produce special versions in other currencies, etc.
“Correntator” serial no. 006800
CBR (Jean Bergmann)/Otto Meuter
Sterling currency version
10 slides, 10 digit display
Flip over front panel for subtraction
Brass & steel
6.4 x 4.7 inches
With leathercloth wallet and stylus
Circa 1925
“Pro Calculo”
Believed made by Otto Meuter
8 slides, 9 digit display
Steel
4.8 x 3 inches
With imitation crocodile skin case & stylus
1920s
“Correntator” serial no. 116492
CBR (Jean Bergmann)/Otto Meuter
8 slides, 9 digit display
Flip over front panel for subtraction
Brass & steel
4.2 x 2.8 inches
1930s probably
Obtained from Switzerland
Produx Counting Machine (Otto Meuter, Germany)
Sterling currency version
7 slides, 8 digit display
Brass & steel
4.6 x 2.5 inches
With cloth backed paper case, stylus and instructions
Late 1930s
On this model the slides protrude from the bottom of the case in use and it is reset by pushing them back by pushing the bottom edge down on the desk.
Back to top.
Produx ‘M’ (Otto Meuter & Sohn, Germany)
8 slides, 9 digit display
Aluminium & steel
6.5 x 3.4 inches
With card case and instructions in German (curiously for the Record)
Missing stylus
Late 1940s probably
Obtained from Germany
FZ EFZET System Produx (Otto Meuter, Germany)
7 slides, 8 digit display
Steel
4.6 x 2.5 inches
With leatherette wallet case and stylus
1940s?
On this model the slides protrude from the bottom of the case in use and it is reset by pushing them back by pushing the bottom edge down on the desk.
Produx Original (Otto Meuter &Sohn, West Germany)
7 slides, 8 digit display
Brass & steel
6 x 2.4 inches
Missing case, stylus and instructions
1950s

A smaller version of the Produx Original above.
“Correntator” made by Unical in Switzerland
8 slides, 9 digit display
Flip over front panel for subtraction (missing)
Aluminium & steel
4.1 x 2.8 inches
1940s/1950s
Obtained from Argentina
The Exactus Mini-Add is the Sterling equivalent, made in England, being identical except for the labelling and the Sterling currency slides.
Produx (Otto Meuter, Germany)
7 slides, 8 digit display
Steel
4.6 x 2.5 inches
Leatherette covered card wallet with notepad
Missing stylus
1930s
On this model the slides protrude from the bottom of the case in use and it is reset by pushing them back by pushing the bottom edge down on the desk.
Record 37755000 calculator (Lucie Meuter, DDR)
9 slides, 10 digit display
Aluminium & steel
8 x 4.5 inches
Complete with case and instructions but missing stylus
1973
Obtained from Bulgaria
Produx Record calculator (Lucie Meuter, DDR)
Sterling currency version
10 slides, 10 digit display
Aluminium & steel
8 x 4.5 inches
Complete with damaged case but missing stylus
“Correntator”
CBR (Jean Bergmann GMBH Berlin NW15)
8 slides, 9 digit display
Flip over front panel for subtraction
Brass & steel
4.2 x 2.8 inches
1930s probably