Why was the Hasselblad 903/905 named so?

Among the Hasselblad V series cameras, the rationale behind the naming of the camera bodies seems to have been based on the maximum shutter speed. For example, the 500/501/503 had 1/500th (leaf) shutter, while the 200/2000 series had 1/2000th, and even the older 1000/1600 series had a 1/1000th speed.

The one exception to this rule seems to be the super-wide SWC series, named 903 and 905. (And since yesterday, the 907X) Does anyone know what the rationale behind that nomenclature is?

My guess is that the angle of view is 90 degrees. Other hasselblad can't have that wide an angle of view.