Re: Determination of Slide Rules

Andreas Poschinger

Hi Meine,

I also have this Ecobra 143. It is named by the way Darmstadt Spezial, not Rietz, and it has more or less a log log layout with trig on slide. For a good usage however a second C scale on the back of slide is missing so that turning the slide is no fun, which is the reason that in my opinion it is no lucky design even if it is one of the rare European models with P on slide.

On my copy so far I remember the numbers are not somehow engraved into the material, but they look out, so it is just the other way round as with normal sliderules. I did not see this on any other sliderule so far and I somehow wonder whether it is really from Germany if it is not a very late model.

Mine came in absolutely new condition. This is why I thought that it was at least bought late in sliderule era, and due to its strange way of characters coming out I thought it was simply very late made, so the last attempt to make them very cheap.

Best regards


Am 19.09.2021 um 20:51 schrieb meine:
I got quite a bunch of slide rules and one of it had no markings at all. However, on a Sunny Sunday afternoon I found out what it was. Here I share my strategy for a 'Determination of Slide Rules'

The slide rule at hand has no markings from the brand or whatsoever and had a simple soft plastic sheet marked 'vendex techniek' (brand 'technical') -- typically 70-ies. Luckily the sheet was still with it ! I like the lower cast letters on those markings :-)

Vendex is the home brand of the Dutch V&D (Vroom en Dreesmann) department store. Vendex sold cloathing, kitchenware, computers, typewriters and school stuff under their own brand. But who made it?

The colours of this pocket-size slide rule are Nestler-like. Or was it Mantissa? Light green. omparing the colours next to eacht other only makes it more difficult -- Nestler's green isn't the same green throughout the years, printed colours and sun wearing over time alike.

The edges of the slide rule are angled -- 90 degrees sharp. More expensive, western slide rules mostly have more rounded edges.

Two indicators somehow pointing to the DDR/GDR.

Searching the database:

Searching the internet for a 'vendex slide rule' gave no results. Herman van Herwijnen's catalog neither.

Slide rule catalogues have a distinct way of writing the scales. So I searched for

'LL3 LL2 A = B CI C = D K LL1' -- an alternative is to replace the = with [ and ] to mark the slide scales. Mind the quote marks to keep the parts toghether in that order in a search engine !

DuckDuckGo and Google came with different results, pointing to the Ecobra 143.
Searching Herman's database on the ISRM ( -- just hit CTRL-F and fill in -- for the scale layout only gave two hits: The 'Ecobra R 143 Rietz' and a 'NoName' -- both were right !

* Ecobra R 143 Rietz

* NoName

Both slide rules are near identical in size, colour and schale order. Only the NoName has a different scaling on the back of the slide and a 15cm scale on top of the body instead of 13cm. Extending the cm scale is seen with many slide rules, so it isn't a big difference.

My conclusion is that this Vendex must be made by Ecobra. This also corroborates with the fact that the Vendex home brand was not the most expensive, but also not really 'cheap', and offering decent quality for a buck ('gulden' that era).


Prof. Dr. -Ing.
Andreas Poschinger

Hochschule München
Fakultät 05
Lothstraße 34
80335 München

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