The Resulta E7 is a small rotary calculator. It has a 7-digit input register, a 7-digit output register, a lever to switch between addition and subtraction, and a clearing lever.
There are 7 vertical slots on the front that reveal what looks like the side of a notched wheel. Next to the slot are the digits 1 to 9. You can insert a stylus next to the digit you want to enter, and pull it all the way down to the bottom of the slot. The wheel then stays in this position. This action sets a digit in the input register at the bottom, and also immediately adds (or subtracts) that amount from the main register at the top. Once you have entered all the digits of the number you are adding (or subtracting), the input register can be cleared and the input wheels reset for the next number by pressing down on the bar below the input register.
There is a small lever on the right front of the machine. If it is pushed down, it will keep the input clearing bar pressed down. This is useful when doing simple multiplications. It allows you to enter each digit several times in quick succession, but of course you can then no longer use the input register for verifying your input was done correctly.
The lever at the top right can be pulled forward and down to reset the main register. Note that the clearing lever can only be used when in adding mode. In subtracting mode it will not move.
To subtract numbers, move the lever on the left to the upward position (push it to the
right to free its catch and then move it upwards till the catch re-engages). The number
wheels in the register will move upwards, disengaging from the input wheels. Instead, an
intermediary set of wheels is engaged with the input. This intermediary set of wheels
causes the number wheels to be turned in the opposite direction by the input wheels.
Simply enter the number you wish to subtract. The input register will display that
number as before, but it is now immediately subtracted from the main register instead
of added.
The clearing lever is blocked from moving while in subtraction mode, so to clear the
register you have to switch back to addition mode first.
There is no serial number, but there is an inspection date scratched on the bottom, in the form MMYY or MYY. In my case it is 763, so it was made in July 1963.
The casing is spot welded together, and riveted to the base. Only the face plate can be removed, giving a limited view of the inside mechanism.
The Resulta was made in the Maschinen- und Werkzeugfabrik Paul Brüning (Machine and Tool factory Paul Brüning) in Berlin from 1927 to 1943 and 1950 to 1969. The first few years it was named the Minerva, only did addition, and had no input register. Clearing the register was done by turning a crank on the right hand side of the machine. It came in two sizes; a 7-digit and a 9-digit register. In about 1930 it was renamed to Resulta, and for a few years after that four main variants were made (with or without input register, with or without subtraction). These were called Resulta A, B, AS, and BS (B = with input register, S = with subtraction). By about 1938 only the BS7 and BS9 models were being made. Presumably the other models were not cheap enough compared to the BS version that it was worth foregoing the extra functionality that the BS offered.
In 1943, the workshop in Berlin received bomb damage, and had to be closed. It took until 1950 before production could be slowly started again, though some other manufacturers had been making licensed copies of the design in the mean time. In 1955, a version was created called the Resulta P7 or P9 that could print the numbers. The normal Resulta BS had seen only minor tweaks in its design since the 1930s, such as improved sound proofing, but in about 1960 the clearing crank was replaced by a clearing lever. The "Export" model, the E7, was simply a repackaged version of the BS7 made for the international market.
Resulta AS flyer
1935
2-sided sheet
159mm × 238mm
The only reference to Paul Brüning I found in online newspaper archives is the notice of the founding of his company.
Here are some of the adverts for various Resulta models from online newspaper archives.
| Patent | Filing date | Publish date | Name | Description |
|---|---|---|---|---|
| DE 538,697 | 3-6-1930 | 20-11-1931 | Paul Brüning Maschinen- und Werkzeugfabrik | Carry mechanism See also CH 158,869. |
| DE 640,417 | 27-8-1932 | 4-1-1937 | Paul Brüning | Restraining device to prevent overruns See also DE 1,693,164 U. |
| DE 1,645,297 U | 19-4-1952 | 16-10-1952 | Paul Brüning Maschinen- und Werkzeugfabrik | Sound damping strip |
| CH 309,226 | 6-12-1952 | 31-08-1955 | Paul Brüning Maschinen- und Werkzeugfabrik | Carry mechanism |
| CH 339,409 | 21-9-1955 | 30-06-1959 | Paul Brüning | Sound proofing |
| DE 1,106,527 | 22-10-1955 | 10-05-1961 | Paul Brüning, Johannes Thiemann | Display shutter See also CH 343,155 |
| DE 1,103,654 | 29-10-1956 | 30-03-1961 | Paul Brüning | Clearance lever |
| DE 1,116,926 | 29-11-1956 | 09-11-1961 | Paul Brüning | Resulta P7/P9 See also DE 1,832,227 U, CH 356,940, FR 1,185,254. |
| DE 1,759,035 U | 28-4-1957 | 19-10-1957 | Paul Brüning Maschinen- und Werkzeugfabrik | Reversing mechanism for ink ribbon |
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