My 12 RD Artar is indeed in Compur II but it's the 49mm throat. And I've never seen a 240 Tele Arton in No. 2. That's news to me. 270mm?
Also, the American shutters like Ilex 3 that are almost identical in throat width are all US threads while Compur is millimeter, so there's no crossover possible to American counterparts.
My mid-60's Schneider literature shows six versions of the Tele-Arton: an f/4 180mm in a I shutter, an f/5,5 180mm in a 0 shutter and an f/5.5 240mm in a I shutter; all specified for 65 x90/ 2 1/4 x 3 1/4. Then there is the f/5.5 240mm in the II 5/2 shutter and an f/5.5 270mm in a I shutter; both specified for 90 x 120/4 x 5. Finally for 130 x 180/ 5 x 7 there is an f/5.5 360mm in a III 7 shutter. Does seem odd the 240 is in a II shutter and the 270 is in a I shutter. Front screw-in thread for the 270 is bigger, 67mm vs. 49mm for the 240. On the other hand rear mount diameter for the 240 is larger, 65mm vs. 51mm for the 270. Overall length is is a bit greater for the 240, 103mm vs. 97mm for the 270. The 240mm weighs more, 800 grams vs. 560 grams for the 270; of course the 240 is in a bigger shutter.
240mm doesn't seem like much of a telephoto for 4 X 5, I wonder how many of these were sold.
David