As to what the source locomotive design may be:
The plans that you show in your last photograph are not directly relevant to this model. It is unlikely that your model is of a French prototype (used in France) as it has a 'pilot' ('cowcatcher' ) which were not (customarily) used in Europe. However, it may be a French design used in the French colonies or areas of influence.
The photograph that you uploaded with three photographs of real locomotives may be more relevant as there are striking similarities (albeit with some stark differences) between the photos and the model. Maybe these photos were taken in Australia?? The signals are distinctive and may aid identification. The paperwork in that photograph may shed some light on your father's inspiration as there is some commentary about the design of valve-gear and I can also see some documentation referring to French 'pacifics'. There is also the corner of some drawings of connecting rods (??) or similar visible, these may indicate the source design.
Your father's model is of a 'Mikado' rather than a 'pacific'. So, any references to pacifics indicate inspiration rather than the specific model.
The model may be a free-lance design incorporating some of your father's ideas rather than a strict copy of a particular type of locomotive.
Model Engineering Clearing House has a good number of Australian based locomotive enthusiasts and one of them may have a few ideas about the model.
Regards,
Phil
Edited By Weary on 10/01/2021 21:49:34