This model was rendered using MATLAB R2016a on the ICQ model of the PSI made by Philip Stooke from the data of the Voyager missions. The original model has a low resolution, so the model was very "poly" look. To avoid this I interpolated it into much more points than the original. It's scaled to 1 in 107 or one in ten million. On this scale the Moon is a basketball, and Mars' moons Phobos and Deimos are 2 and 1 mm respectively. It's also scaled to 1 in 4 x 106 or one in four million and 1 in 2 x 106 or one in two million.
The file's names explained: name_1_x_10_y.stl is 1 : x * 10y. So _1_6_10_7 is 1:600000000 or one in 60 million.
Proteus wasn't part of the original Neptunian System. Like other inner moons of Neptune, it was probably the result of the accretion of the fragment from the original moons of Neptune, shatered by collisions or gravitational interaction when Triton was captured.
Orbital period: 1.122 d.
Composition: Icy body. Rubble pile
Density: 1.3 g/cm3.
Dimensions: 424 km × 390 km × 396 km
Model scale: 1:1x107 (4cm) 1:4x106 (10cm) 1:2x106 (20cm)
Triton (behind), Larissa (down left) and Proteus (down rigth) in the same scale.