Slide rule workshop N

Jean Paul Hild's mystery slide rule No. 1

Nestler

Click images for magnification

Nestler front
Nestler front
Nestler back
Nestler detail

Questions:

  1. When was it manufactured ?
    Seems to be of SOHO type but I couldn't find other Soho rules from Nestler.
  2. Why are the scales deferred ? (see picture)
    Andreas Faßbender has provided an extensive report