Facit calculators work on a similar principle to the more conventional Odhner type pinwheel calculators, but their external appearance and user interface is strikingly different.
Rather than having an external moving carriage in conjunction with a fixed rotor, Facit machines reverse this arrangement and the carriage is fixed but the rotor moves. Numbers are entered into the pinwheels with numbered keys rather than by directly setting the pinwheels by hand. The user interface has advantages and disadvantages compared to the Odhner type of machine. One advantage is that number entry is quicker and less prone to error; a major disadvantage is that the input register needs to be completely cleared in order to enter a new number, making the machine unsuitable for procedures which rely on iterative modifications to the input (such as Töpler’s square root algorithm).
Facit machines seem to be less common than Odhners on eBay. But Serial Number evidence points to many more Facit machines being made. The obvious conclusion is that Facit machines are more fragile or less easy to repair than Odhners, so fewer machines have survived.
Facit Model TK
Serial No. 182923
Price Paid (including postage): £30
The Facit Model TK was in production between 1936 and 1954. It replaced the Model T, to which it is very similar; the main difference being the provision of a feature called sliding quotient coupling, which enables the dividend and the divisor to be input without the requirement to pad them out with zeroes.
This machine was only slightly different from its direct successors (Models NTK and C1-13), which except for minor mechanical refinements and styling changes, were essentially the same. Thus it can be said that a design from the 1930s was produced without interruption with only slight modifications until the early 1970s – a remarkably long time.
Facit Model NTK
Serial No. 472198
Price paid (including postage): £107.50
The Model NTK was in production between 1954 and 1957. It replaced the Model TK, and was succeeded by the Model C1-13, which were functionally identical (and very similar mechanically). This particular machine is in nearly mint condition, and came with a carrying case and two instruction manuals. This is the most expensive machine I’ve ever bought – it cost me £100 plus £7.50 postage. Instructions for operating this machine can be found on the User Guides page here. Despite its short production run, Facit managed to churn out approximately 55,000 Model NTKs, and they are among the most readily available to collectors, and every collection should have one (or a Model C1-13).
Facit Model C1-13
Serial No. 816703
Price paid (including postage): £16.40
The Model C1-13 was in production between 1957 and at least 1970, and the evidence from serial numbers shows that in excess of 400,000 of these being made – a truly staggering number. Again, there are plenty of these available to collectors, and they can be obtained quite cheaply.
Facit Model C1-13 (Later Version)
Serial No. 869323
Price paid (including postage): £21
This machine represents a stylistic change to the Model C1-13, which probably deserved a change of model designation but didn’t get one. The main difference is that the cover is of a one piece construction.
Facit Model LX
Serial No. 104346
Price paid: £11
This large capacity machine, of which approximately 11,500 were made, was in production between and 1954, when it was succeeded by the Model NLX. The machine is similar to the Model TK, but with the refinement of the accumulator and counter registers being contained within a sliding carriage, enabling the capacity of the machine to be increased without massively increasing the size and weight of the machine.
Facit Model NLX
Serial No. 501960
Price paid: £0.99
The model NLX was produced between 1954 and 1956, and only 2360 were made. The main difference between this machine and it predecessor is that the lever to clear the input register operates horizontally rather than vertically.
This example was a bit grimy and very stiff to operate when I bought it, but it cleaned up beautifully, and operates very smoothly.
Facit Model NEA
Serial No. 408291
Price paid (including postage): £43.45
The Model NEA, produced between 1943 and 1956, is essentially a motorised Model NTK. This particular machine was one of the last to be made before the model was superseded by the Model CS 1-13.
It can perform fully automatic division, and semi-automatic multiplication. The result register and revolutions counter are cleared manually with the levers on the left, whereas the input register is cleared electrically. This particular machine was bought from Germany on eBay (half of the purchase price was spent on postage). It was initially jammed, but by sheer luck I managed to get it going, and it now performs flawlessly.
A video of the machine (with the cover removed) can be seen here, performing the division 355/113, which equals 3.1415929.
Facit Model CA 1-13
Serial No. 655319
Price paid (including postage): £43.45 + £20 for a replacement outer casing
The Model CA 1-13 can perform both multiplication and division fully automatically. This particular example, is somewhat of a hybrid – the outer casing of the machine was damaged in transit, so a non-working machine of a slightly later vintage (1965) was bought as a casing donor. The machine pictured is in full working order, and a video of it working (with the cover removed) can be seen here.
A subtle difference between the 1958 and 1965 versions of the Model CA 1-13 was that numbering of the input and result registers was reversed. Fortunately, this meant only that the key caps for the I and III register clearing buttons required swapping over.
Facit Model CM2-16
Serial No. 1030816
Price paid: £10
This (rather heavy) calculator marries a modern calculator style keypad with a traditional pinwheel calculator. In operation it is similar to other manual Facit machines, but unlike other Facit machines it features a Back Transfer mechanism. Not only that, but numbers can be transferred from either the result register (accumulator) or – somewhat unusually – from the revolution counter, depending on the position of the rotor within the machine. Indeed, with careful placement of the rotor, numbers can be transferred from the right hand side of the accumulator and the left hand side of the revolution counter. This is probably not a useful feature!
One useful feature of earlier models was that a sliding plate would cover the unused digits in the input register as it was moved to the left during multiplication. This refinement was dispensed with in the CM2-16, presumably because it was difficult to implement while including the back transfer capability.
The operating instructions for this machine can be found on the User Guides page here.
Facit Model CM2-16 (Later Version)
Serial No. 1089413
Price paid (including postage): £40 including the Brunsviga 13RK
This machine exhibits minor differences when compared to its earlier version – the plastic letters that spell out FACIT on the rear of the machine are square rather than circular, and the leftmost of the two right hand arrow buttons has lost its “16” legend, presumably because it was thought to be confusing.
Facit Model 1004
Serial No. 1930233
Price paid: £5