ordinates are linked by a straight line, whose intersection with the spacer column gives the spacer thickness. Could a lack of such methods be the cause of problems in the Norinco-Kunming 20 and 40 x 100 that everybody were selling a while back.? The Cloudy Nights site seems to be the only independent source of info about these.
That sounds like a very nice nomograph. I will post a copy if anyone can send the citation.
Subject: New review by Merlitz
Review: 10x50 Swift Kestrel vs. Zeiss Jenoptem vs. Hensoldt Diagon
by Holger Merlitz
Subject: Kershaw Binoculars
I am trying to date two Kershaw 6x24 binoculars. Both are of the early style with hinges that are integral with the prism cover plates. These are civilian glasses that were donated to the war effort but are identical to the Bino Prism No.3 Mk II shown on page 147 of Dr. Rohan's book. It is my understanding that this model was manufactured from 1909 until sometime in the 1930's. Being civilian binoculars, they have no manufacture dates on them. The first binocular is inscribed "A. Kershaw & Son Ltd. Leeds" with serial #N3881. The second has the name KERSHAW within an oval with "6x" over it and the serial #11922.
Both binoculars have identical large squared-off yellow Admiralty broad arrows inlaid into the textured body covering. Number N3881 is also marked with very large broad arrows on the cover plates next to the objective lenses. These are type "f" on page 139 of Dr. Rohan's book. They are inlaid with raised white metal. The book "Barr & Stroud Binoculars and the Royal Navy" (page 125) by William Reid indicates that this type of broad arrow was associated with Britain's National Physical Laboratory during the WW1 era. This may be sufficient to date #N3881 in the 1909 (start of manufacture for this model) to 1918 range. This specimen is in good condition appearing to have never been overhauled.
The second binocular (serial #11922) has no military markings other than the yellow broad arrows. It is in excellent, close to mint, condition. It just looks too new to be from the WWI era. The inlaid yellow arrows are dimensionally identical and appear to be made of the same celluloid plastic. The inlay technique is also identical for both binoculars. The celluloid on #N3881 has darkened somewhat with age while the arrows on #11922 are still fairly bright. Please note that this is not the style of arrow seen on WW2 vintage Barr & Stroud CF25 and CF41 binoculars. Nor is it like those seen on the Canadian R.E.L. glasses. The arrows on the B&S and R.E.L. binoculars have rounded ends and look like they were cut into the body covering with a milling machine. This type of arrow seems to be typically filled with yellow paint, not celluloid. The arrows on my specimens are neatly cut into the covering and have sharp square ends.
The big question is this; Was the yellow squared-off celluloid inlaid broad arrow marking used in both World Wars? If it was not used in WW2, did it continue to be used for any period of time after WW1 and if so for how long? Any help with this would be greatly appreciated. Thank you.
Regards, John Anderson