Bit off topic but my excuse is that Drew did bring up a reflector sight.
Shortly before the Second World War when reflector sights were being introduced for the new Hurricane and Spitfire fighters, the Air Ministry was a bit stuck to get them into production but placed a contract with Goerz the well known optical factory in Austria. Hmmm? What could go wrong?
Shortly afterwards, Anschluss! Hitler marched in to Austria.
Goerz, to their credit (and probably at some risk to their personal safety) quietly fulfilled the contract and shipped the goods.
As a result about half the British fighters in the Battle of Britain were using gun sights made in the Third Reich.
Another story, might be apocryphal, is that the sights were very hush hush and that when a German Luftwaffe officer was making a courtesy visit to a British squadron before the war the pilots were told to feign stupidity and not know how they worked.
On this happening a R.A.F. Brass hat climbed up next to the cockpit and gave a full explanation.
