With many thanks again to Anthony, I now have more scans of several Challenge Timer models from Citizen’s old catalogs. These are especially good for checking ‘correctness’ of examples for sale, things like the colour of day and date wheels, original bracelets and straps, and dial and hand combinations. I’ll add these to the reference page with some commentary but in the meantime here are the scans for your information. First, from 1974:

This image includes a rare (non-chronograph) 6501 automatic, with rotating inner bezel. I was surprised to see that the original price was more than the Challenge Timers. These original black straps are extremely rare these days – I have only seen one or two examples of them on Yahoo Japan.
Now, from 1975, with the 67-9119 shown on its familiar bracelet with black panels:

Nest is from 1976, and with the same models as 1975. But I’ve included it because there is one interesting difference (and it’s not the position they are in on the page). Can anyone spot what it is?

With the 1977 catalog featuring the same modes as ’75 and ’76, let’s move on to 1978, and here we have the ‘Speedies’:

And finally, five years later in 1983, we see two examples of the Walter Wolf special edition, one in a titanium case. And look at those prices!:
