arrow indicationg spin direction on frontloader washers

[askomiele]

I was watching some youtube videos while I noticed that on some frontload washing machines (older domestic and industrial machines), the direction in wich the washer is spinning during extraction is indicated by an arrow. Sometimes its a sticker on the door or molded in the glass of the door (Miele WS see video) Anyone knows why that is?

 

[whirlykenmore78]

Arrows on washer doors:

IIRC this is to check spin rotation to be sure a 3 phase machine is wired correctly.