Does anybody on the forum own and use this lens.Its production is surrounded in mystery and judging by its extreme rarity it would seem that it was produced in very small numbers perhaps one batch of only 250 lenses.It is a British, late 1940's(?) or early 1950's lens, which is in a Cook and Perkins(marked accordingly) focussing mount and barrel and is very similar to the more easily acquirable 50mm (2") f/2.0 Taylor,Taylor & Hobson lens fitted also in a Cook & Perkins mount which was fitted as standard to the Reid cameras produced by Reid & Sigrist in Leicester,England.Some literature suggests that the National lens is a clone of the Taylor,Taylor & Hobson lens but this fact is still to be researched and resolved and as far as I know the optical formula of the National lens (Elements/Groups) is unknown. The lens serial numbers engraved on the lens ring are 354xxx and the last three digits xxx are engraved on each individual lens barrel which probably means that each lens cell was matched to its own particular barrel. My lens is 354160 and I only know of one other 354204 at the present time. The barrels are also engraved with various British and U.S.Patents, and I understand that the British Patents refer to the mounting of the lens cell and not to the optical design,the details of the U.S.patents are not known to me. British patents:-377537,461304,507184,587090. U.S patents:-1955591,2117251. If anybody has any further information or owns and uses this lens I would be very interested to know.