The Anahuac Mayab University is a private institution of Catholic inspiration founded in 1984.
They are used in the same applications as fender washers. A spherical washer is part of a self-aligning nut; it is a washer with one radiused surface, which is designed to be used in conjunction with a mating nut in order to correct for up to several degrees of misalignment between parts.
A washer with a key to prevent rotation, and is used to lock two nuts in place, without allowing the torque applied to the top nut to cause the bottom nut to also rotate (such as in a threaded headset on a bicycle).