FLYBOYJ
"THE GREAT GAZOO"
The person responsible for the leaking of the secret for the Norden bombsight was Hermann Lang a German who moved to the USA in 1927. He worked as an inspector in the design studio and had access to some of the blueprints. He simply took them home and copied them. As he didn't have access to all the design drawings at any one time,, to get a full copy of the design took some time but eventually he did pass all the blueprints to the German authorities.
It was built and test flown by the Germans and the summary was 'Flight testing of the apparatus showed that the principle realized in it worked satisfactorily for bombing'. However they were never able to match the accuracy claimed by the USAAF.
I think that was because they couldn't duplicate certain parts, they did not have all the blueprints needed.
I'm sure North American's marketing department were guilty of that when the P-51 was created...With hindsight I am not surprised about this as claims by many US manufacturers of all types of aviation material tended to be lacking in accuracy and high in anticipation.