I've posted a pic of the Spence Wolf "Alpine" derailleur modification at the below URL
this is the actual unit from which David's copies were made.
Between this cool re-pop and Mr. Broderick's Mafac brake plates, it's safe to say that Spence's good work lives on. There could be few better tributes to the man; He was a genuine good soul.
Bainbridge Island, WA