Is it definitely an f5.5 Xenar ? If so it's an interesting lens, I have a rare f5.3 165mm CZJ Tessar these are higher quality in terms of overall sharpness compared to the more common f4.5 Xenars and Tessars but not as slow as the highest quality f6.3 Tessars.
A few years ago I tried to identify a few of my 9x12 cameras, I made a list of those for sale on Ebay - make, model, lens, shutter and that's how I narrowed your camera to possibly being a Zeca

. I think the Zodel (wallace & Heaton here in the UK) 9x12 cameras were re-badged Zecas, re-badging was very coomon before WWII.
If you can PM or email photos of the camera back with the focus screen holder removed and the reverse side of the back as well I may be able to help with the holders you need.
I have quite a few Rada and Rollex 6x9 roll film backs for 9x12 cameras(pre WWII), after WWII Plaubel owned Rada and Linhof Rollex. One Rada back is still in its original water damaged box. I suspect Duplo is referring to the bellows double extension, usual for better 9x12 cameras only the cheapest were single and very few triple, that's extension compared to the focal length, so dounle focusses to 1:1, triple is only found where lenses are interchangeable.
Ian