It originated from the single key of the 1st SS Pz Div. The commander of the Div and later the SS Pz Corp was Sepp Dietrich, who's name translates to picklock or skeleton key.
The Oakleaves were added when Dietrich got the Oakleaves to his Knights Cross.
I am a Norfolk man and i glory in being so
On the bench: Airfix 1/72nd Harrier GR.3/Fujimi 1/72nd Ju 87D-3