When I worked at Data General (a long time ago)
We once had a new director who informed us that we would be having "Casual Fridays". As an engineering group, we had never heard word one about dress, the implication being, that if all the naughty bits were covered and you didn't smell too bad, you were good.
Our group arrived Friday morning dressed in our "interview suits". Nothing more was heard about the matter.
// a photo was taken...I run across it occasionally