User Guides

Click on the links to access the user guides.  I believe them to be out of copyright, but if this is not the case I will remove them if requested by the copyright owner.

These are scanned copies of originals in my possession.  If you would like a higher resolution scan, please contact me at

Multiply and Divide on an Original-Odhner

This manual can be dated quite accurately to 1950, because the featured model range includes Models 127 and 129, but Models 137 and 139 have yet to replace Models 37 and 39.

The manual is applicable to almost any model of Odhner pinwheel calculator,with the proviso that the quick rotor clearing system is located differently on 200 Series machines (see the Original Odhner page for details).

The manual is also applicable to any Odhner type of pinwheel calculator, except that there will be differences in operation particularly with regard to clearing the registers and back transfer (if present).

Facit NTK Calculator Manual

This manual came with my  1955 vintage Facit Model NTK, and is in fact dated 1954.  It is applicable to all manual (non-electric) Facit machines with very little adaptation.

Facit C1-13 Calculator Manual

This is essentially the same guide as that for the Model NTK, but shows the ‘new’ machine.

More Ways To Get The Most Out Of Your Facit

This booklet is dated 1952, and contains calculation exercises and examples for Models TK, NEA and ESA-0.  The examples work just as well with Models NTK/C1-13, CS 1-13, and CA 1-13 respectively.

Facit CM2-16 Calculator Manual

This manual is dated 1959, and contains pretty much the same examples as in the Model NTK manual, but includes examples of the use of the back transfer facility .

Monroe Calculator LN Series Manual

This manual is dated somewhat later than my Monroe machines, but the LN Series machine illustrated in the manual is identical in operation to the preceding L Series machine.

Monroe Automatic Calculator CSA Model Operating Instructions

I don’t actually have a Monroe Model CSA, but someone might find this useful.

Muldivo Mentor Instruction Manual

This is the instruction manual for the Muldivo Mentor, known outside the UK as the Walther WSR160.  Although fairly brief, it does include a square root algorithm.

Operator’s Manual for Busicom HL-21

This manual is written in a style reminiscent of Japanese camera instructions of the period, but is fairly comprehensive.

Der Kurzeste Rechenweg auf der Facit

This is essentially a German version of  More Ways To Get The Most Out Of Your Facit.  Examples are given for machines C1-13, CS1-13 and CA1-13, which are equivalent to earlier models NTK, NEA and ESA-0.

The following two-part document isn’t a user guide as such, but it’s an exercise book used by someone who went to a comptometer school.  Unfortunately, I don’t know who this person was, but it was the mother of the person who sold me the 1950s Sumlock comptometer.

Comptometer School Exercise Book Part 1

Comptometer School Exercise Book Part 2