An indication of the general hardware type of the physical
entity.
An agent should set this object to the standard enumeration
value which most accurately indicates the general class of
the physical entity, or the primary class if there is more
than one.
If no appropriate standard registration identifier exists
for this physical entity, then the value 'other(1)' is
returned. If the value is unknown by this agent, then the
value 'unknown(2)' is returned.