Series of photos showing the setup and use of centering scope on a Deckel 
FP3.  Part to be done is a shift rod from an Alfa Romeo 2900B  transaxle.
Rods assembeled in box and  forks positioned  to give correct gear engagement. 
Position of forks marked by small drill through threaded drill bushing in each fork. 
Centering scope used to find real center of marking drilling.