Greetings Train Tech,
I finished this a couple of months ago, but I've only just got around to posting it.
This unusual locomotive was designed in 1900. The Gr670 is a compound locomotive, featuring two high-pressure cylinders on one side and two low-pressure cylinders on the other. While a cab-forward design seems like a logical way to build a locomotive, it doesn't seem to have been that popular, presumably due to logistical challenges, such as where to store the fuel (note the giant coal bunker behind the cab, overlapping the boiler). The Gr670 was apparently nicknamed "Mucca", meaning "cow".
The locomotive is essentially two trucks (one containing the pistons and the drivers) pivoting under a rigid body. It took some messing around to find pivot locations that allowed the locomotive to clear curves without the flanges of the drivers scraping against the boiler.
The tender is probably my favorite part of the model. The cab-and-tank appearance of the tender echoes that of the locomotive, lending weight to the theory that the locomotive was nicknamed "mucca" because the locomotive and tender together reminded some observers of a cow and calf.
And some video:
Full Brickshelf gallery
More info on the Gr670
Wikipedia article (Italian)
Let me know what you think!