Need help in IDing a lens.

Sironar
Sironar f5.6 In 2/1968, it was made in 100mm for 6.5x9cm; 135mm for 9x12cm; 150mm for
9x12cm or 5x4in(?); 180mm for 13x18cm; 210mm for 13x18cm and 240mm for 18x24cm and other sizes such
as 300mm and 360mm were 'in preparation'. They cover 60° at f5.6 or 70° when slightly stopped down. The
front cell can be used on its own as a slightly soft focus lens or somewhat stopped down as a sharp long
focus of 3x the focus.
This was normally made in large format foci, such as 150 and 210mm which are those usually seen. It
was a standard large format lens for studio and architecture, and was made to an air-spaced Dagor design
(roughly Q20) and is optically excellent. The front mount is or can be very large and impressive, the 150mm
lens taking c.70mm external filters. The coating at No8,723,58x is also very impressive making for a premium
quality item. (Sadly a number sold in the UK including the last example, seem to have suffered from a faulty
supply of balsam, and have separated. One report has been that this actually did not affect the performance
seriously as with the example seen and the lens was regularly used in spite of it: but it must reduce the value
of the lens considerably. A repairer says that rebalsaming here is not normally possible. In addition, the
Compur electronic in the last example had failed, and only offered Time and probably 1/500sec. Thus they are
an item to purchase only with care if for use.)
Sironar-N f5.6 This was made in 100, 135, 150, 180, 210, 240, 300, 360, 480mm at least.
This probably is a redesign with new glass, and seems to be an excellent lens. It was among Rodenstock
lenses featured in Modern Photo 06/1980 p10advert. for 100-360mm and 72°, with multi-coating and improved
color correction.

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