US NAVAL GUN FACTORY OPTICAL SHOP 10x45 Mark VI WW2
Showing one of the extending eye-shields pulled out.
This is a pair of US Naval Gun Factory (NGF) Optical Shop Annex 10x45 Mark VI binoculars. They are a modification of the WW1 Type E 6x30 binocular, with extended and flared objective tubes boosting magnification to 10x. I have seen one example with British Government broad arrows on the top prism covers, of a pattern used by the Royal Navy so some were apparently supplied on Lend-Lease.
On the left top prism cover is “Bureau of Ordnance/10x45/US Navy/Mk VI/No 943”; on the right prism cover “US Naval Gun Factory Optical Shop Annex” with the fouled anchor logo and “Rochester New York”.
The US Navy Board of Ordnance was responsible for int. al. the supply of optics for gunnery. The No 943 is likely an inventory number. On the front face of the forward bridge arm is a serial number 664293. The objectives have pull out eye-shields.
The binoculars are in fairly good condition, mechanically, optically and cosmetically; viewed through the wrong end, there is a chip on each prism, but these do not affect viewing in use. I have seen some examples on the net with thumb wheels to deploy built in yellow filters. It is possible that these were models originally fitted with such eyepieces, as 6x30s. Versions of this binocular are also seen with brown leatherette covering.
Early in the war, in 1942, following heavy losses in men and shipping in surface engagements with the Japanese Imperial Navy, the need was identified for higher power hand held binoculars than the standard 7x50, for naval gunnery fire control officers. This resulted ultimately in the conversion by the USNGF Optical Shop Annex, of Bausch & Lomb 7x50s to a 9x63. It seems likely that the 10x45 was similarly converted for the same reason, but this gives an exit pupil (the radius of light reaching the eye) of 4.1 (45 divided by 10), with an exit pupil of around 7 considered optimum for poor light. The 10x45 was declared obsolete in 1944.
Under the US NGF Optical Shop logo and designation, is “Rochester NY”. The NGF Optical Annex took over the civilian Crown Optical Company factory in Rochester in 1917 when Crown could not keep up production for the US Government. In 1919 the Optical Shop moved to the Washington Naval Yard and remained there. I have only ever seen NGF binoculars marked “Rochester NY”. Since this is a converted 6x30 E, it probably dates from the Rochester days.
US NAVAL GUN FACTORY OPTICAL SHOP 10x45 Mark VI WW2
Showing one of the extending eye-shields pulled out.
This is a pair of US Naval Gun Factory (NGF) Optical Shop Annex 10x45 Mark VI binoculars. They are a modification of the WW1 Type E 6x30 binocular, with extended and flared objective tubes boosting magnification to 10x. I have seen one example with British Government broad arrows on the top prism covers, of a pattern used by the Royal Navy so some were apparently supplied on Lend-Lease.
On the left top prism cover is “Bureau of Ordnance/10x45/US Navy/Mk VI/No 943”; on the right prism cover “US Naval Gun Factory Optical Shop Annex” with the fouled anchor logo and “Rochester New York”.
The US Navy Board of Ordnance was responsible for int. al. the supply of optics for gunnery. The No 943 is likely an inventory number. On the front face of the forward bridge arm is a serial number 664293. The objectives have pull out eye-shields.
The binoculars are in fairly good condition, mechanically, optically and cosmetically; viewed through the wrong end, there is a chip on each prism, but these do not affect viewing in use. I have seen some examples on the net with thumb wheels to deploy built in yellow filters. It is possible that these were models originally fitted with such eyepieces, as 6x30s. Versions of this binocular are also seen with brown leatherette covering.
Early in the war, in 1942, following heavy losses in men and shipping in surface engagements with the Japanese Imperial Navy, the need was identified for higher power hand held binoculars than the standard 7x50, for naval gunnery fire control officers. This resulted ultimately in the conversion by the USNGF Optical Shop Annex, of Bausch & Lomb 7x50s to a 9x63. It seems likely that the 10x45 was similarly converted for the same reason, but this gives an exit pupil (the radius of light reaching the eye) of 4.1 (45 divided by 10), with an exit pupil of around 7 considered optimum for poor light. The 10x45 was declared obsolete in 1944.
Under the US NGF Optical Shop logo and designation, is “Rochester NY”. The NGF Optical Annex took over the civilian Crown Optical Company factory in Rochester in 1917 when Crown could not keep up production for the US Government. In 1919 the Optical Shop moved to the Washington Naval Yard and remained there. I have only ever seen NGF binoculars marked “Rochester NY”. Since this is a converted 6x30 E, it probably dates from the Rochester days.