British AIR MINISTRY WWII Brass Wide-Angle Lens with F/4 and F=5 Inches

Description

British AIR MINISTRY WWII Brass Wide-Angle Lens with F/4 and F=5 Inches
British AIR MINISTRY brass wide-angle lens with F/4 and a focal length of F=5 inches. These lenses were manufactured for the Royal Air Force during WWII by the British optical industry (including Dallmeyer and Ross) under contracts let by the Air Ministry. Wide-angle lenses were likely used for reconnaissance aircraft.
The lens has no manufacturer's marking. It does have a REF. No. 14A/1101 marking which likely refers to the contract number. Serial number is 168 427 (on front and back elements). Diaphragm operation from 1:4 to 1:11.
The lens is in good cosmetic condition. Glass is clear, there is a small scratch in the center of the rear element. Diaphragm operation is smooth (no oil on the blades).
To judge the performance of the lens (and out of curiosity), I mounted it to a 24 MPixel Nikon D7100 digital camera via a Leitz focusing bellows arrangement. The Nikon camera was set aperture-priority auto-exposure, and manual focus. The camera was mounted on a sturdy Majestic tripod (see picture #8 for the set-up). The lens was manually focused on the LED lights in a street lantern about 100 yards away.
The results are shown in picture #9 for diaphragm setting of 1:4, picture #10 for 1:5.6, and #11 for 1:8. The insert at the upper right corner shows a full resolution detail. At the diaphragm setting of 1:4, there is some softness which disappears already at 1:5.6. Not much improvement at 1:8. The results demonstrate that the lens is capable of high-quality results.
Buyer to pay actual USPS shipping cost (no handling fee). Estimated shipping weight is 2 pounds.
I would be happy to combine several items in one shipment to reduce shipping costs. Happy bidding!