The subtraction ring on my Type II #523678 is black. Or rather, there is none. Not red, white, orange or plain metal. There is a small sliver of what is probably red paint, but not enough for me to be sure.

Are there any handy lists or other pointers for determining the correct colour ? Google is not great at finding this sort of detail.

I plan to mask off and airbrush the colourred ring back in situ. I am not worried about the exact shade. This unit will always look used, so evidence of running repairs does not bother me.

Here is a comparsion


[black Curta II]


[early grey Curta II]


[later grey Curta II]

Maybe you have a Curta II with the brighter red/orange ring (the middle of the samples). This color is very brittle - so it's likely that the color was lost.

>>> The complete comparsion of the three Curtas Type II (use the arrows on the top left for navigation and select the type below the pictures...)

There is no list - you can only identify similar variants of all these produced Curtas and define some categories.

Thanks again.

Mine matches the 'late grey' pictures. A plastic crank and red sliders on every third digit. Your photo shows where the red paint needs to go.

Using some 'British Rail Signal Red' and a small brush, job done.

I am sure an expert would immediately spot the difference, but all I needed was the red ring to serve its initial purpose, to indicate between 'add' and 'subtract'

My 14 year old nephew must have some appreciation for mechanical things. His first question was to ask how many parts there are. I have seen 600+ for a Type I, anybody have a count for a Type II ?

For the plastic crank with red ring, I used the glossy red from "Humbrol" with excellent results. As a special paint for plastic models it worked perfectly with a super fine brush, and hopely it will keep in place for a long time. No masking needed, just whip off any excedent.