Perhaps one of the lens guru's can shed some light on this. I recently acquired a couple of barrel type G-Claron lenses. A very nice, but ordinary 210mm and a rather older and more interesting 355mm lens. This is clearly marked G-Claron on the outer part of the front cell, with serial # 10737773. It is mounted in a chromed brass barrel, also marked 355, with aperture scale from F9 to f90. When I unscrewed the cells to inspect them, I was surprised to find that both front and rear threads were 55.7 mm. From previous threads, I undertood that the earlier, 355 G-clarons had threads of 67mm in diameter. Any ideas, is this the famous missing "Dagor" style, 355?