I did some research, and learned (again) something new regarding M* EMD F7 models.

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(1) Shell details: According to ModelRailroader October 2006 pg. 60 - 65 drawings, the M* model is a F3 Phase IV / F7 Phase I. Those versions had, inter alia, a rectangular connection door window and a a triangular roof overhang (thus no M* invention). Only subsequently, the connection door window became round and the roof overhang disappeared. For comparison and confirmation, see also: http://www.atsfrr.net/re...funits/pdf/F7-A-Pass.pdf

(2) Undercarriage dimensions: I am astonished and positively surprised that - despite common statements - M* F7 models do not fare that bad in comparison with the prototype (let alone competitors).

axial distance
prototype: 2744 mm
1:87: 31,54 mm
Märklin: 34 mm

truck distance
prototype: 9144 mm
1:87: 105,1mm
Märklin:106 mm

Length
prototype: 15443 mm
1:87: 177,50 mm
Märklin: 178 mm

Width
prototype: 2997 mm
1:87: 34,44 mm
Märklin: 36 mm

The tolerances are in my view totally acceptable (and impressive given that the M* F7A form stems from the 1960s).

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In summary, the model is better than its reputation.