Ross Xpres 12" f/4.5

Ross London was a maker with a venerable history going right back to 1830, before photographic lenses were a thing, and they were the most significant lens makers in England until around 1860.  In the later 1800s they were an obvious choice of manufacturing partner for Zeiss of Germany, and were licensed to make a number of Zeiss designs.  This stopped with the outbreak of war in 1914, and soon after the Xpres line of lenses was introduced, initially for aerial surveillance.  It is said that the design is based on the Zeiss Tessar but with 5 elements instead of 4, so as not to infringe the patent.  In any event it was a mainstay of the Ross range in the 1920s and a fine performer.  

This example is from that era and is a great all-purpose lens.  Wide open it is very sharp in the middle with a dreamy low-contrast look, perfect for portraits, with interesting swirly bokeh, similar to a Petzval lens.  Stopped down it becomes sharp all over and contrast increases significantly.  Ross Xpres lenses are relatively plentiful and inexpensive, but definitely worth having, and very adaptable to Pete’s guillotine shutter.  Shown above it’s on a tilting mount with behind-the-lens shutter block.  It’s a chunky black-painted brass lens with many aperture blades, a big favourite.