This catalogue which I believe dates back to 1937 shows duplex models:
I think they were used a lot by Army officers and the Doctors for all the different inserts that were available back then.
Here is another one from more recent times, it was produced as a limited edition of 1921 examples and sold as part of the 85th anniversary of Filofax, I saw this one at Filofax in Burgess Hill when we visited them back in September last year.
I was looking back through some photos and some previous posts when the thought occurred to me that would a duplex organiser partially solve the desire for bigger rings in a personal size organiser? I have 30 mm size rings in a few of my own organisers, but nearly all in the current range these days are 23mm and there are the odd exceptions like the Gillio medium size which has 26 mm size rings.
But if you had two sets of 23 mm rings would they be the equivalent of a set of 46 mm rings? That's 1.8 inches in olde worlde measurements!
Then I spotted a link in the comments to some modern day duplex organisers... I had to investigate.
And this is what I found
Yes this is made out of a very thin flexible PVC, not exactly luxury, but for the purposes of this assessment of the idea of two sets of rings it is fine. I bought it from 'Kit Monster' and it's sold for holding Tactical Aide Memoirs (TAM)
I've done a video about it too.
Looking at it over a few days I've been trying to understand why they spaced the rings so that the pages over lapped, why not space them a bit further apart so they didn't overlap?
I might be tempted to make something similar to this out of a single piece of leather but make it a bit bigger and have a simple closure on it to hold it closed.
The one advantage I can see with a duplex is that you can have two sections of your organiser open at the same time and it is then easier to refer to both sections without having to flick from one to the other. But of course is does take up a lot more desk space in the process!
Are there any of you that have used a Filofax duplex organiser on a regular basis?