You mean this one?

Then everything should be clear, those were indeed the broad gauge shovel noses of the former Ferrocarril General Mitre.
The GE export list lists them as:
Country: Argentina, Ferrocarril General Mitre
QTY: 25
Numbers: 5501-5525
Build No.: 31060-31084
Model: 115T
HP: 1500
Engine: Alco 12-244 G
Gauge: 1.676m
Axles: C-C
Year: 11/53-3/54
http://www.tamr.org/Andy_Inserra/ALCoXportRoster.pdf lists them as "5GE731D6" (but with the correct GE model type: 115T)
OK, if this is sufficient, let´s move on.
Please give country, name of railway, name of builder, and class.
regards
Michael