Voigtländer remained independent after the War, when hard times (due in part to the effects of War reparations on Germany's economy) caused some other firms to enter mergers.In 1920, Rudolf Heidecke and Paul Franke, employees of Voigtländer, left the firm to form Franke & Heidecke (their first camera, the Heidoscop, bears a striking similarity to Voigtländer's Stereflektoskop; Heidecke was a designer, and it seems likely that he either had rights to this design, or had Voigtländer's blessing to use it).
A list of serial numbers can be found here should you wish to date your Rollei.
The picture above shows the easiest way to tell the T model from a distance, it is the only Rollei with the shutter button on the side.
During this time parts of production were moved to the Wolfenbüttel district (still on the outskirts of Braunschweig), where prisoners of war were employed.
In 1956 Schering sold its shares in Voigtländer to Carl Zeiss.
In 1925, Schering AG (a chemicals company) bought a majority share in Voigtländer. It was in the period of Schering's ownership that many of the familiar Voigtländer cameras were made, including the first Bessa.
Voigtländer again made military equipment (including but not limited to aerial reconnaissance cameras, binoculars and rifle scopes) for Germany's rearmament and the Second World War, but continued development of cameras at least up to shortly before the War itself; the Bessa 466 was designed around 1938 (Voigtländer's British patent for this innovative camera was finalised in 1940, actually during the War)!The lens, with the widest relative aperture of any then made (about f/3), was very successful for its intended purpose: the making of daguerreotype portraits.The wide aperture allowed a very considerable reduction in exposure times.Even though the camera is positioned between the budget 'cord and the pro 'flex it certainly has more of the Flex's 'genes' I've often seen people give the advice to get a Rolleicord over the T as the lenses are pretty much equal and the cords are cheaper, I'd advise that prospective purchasers should get a T as they are much better in daily use.Below is one of the main reasons I prefer the T to my Rolleicord The view above graphically illustrates how much brighter the T is compared to a similar aged Rolleicord, no doubt later Cords have better screens but I've always found them duller and slower to focus.The lens has four elements, divided in two groups, the two front elements cemented, the two back elements just placed close to each other.