Questions about Mettler Office Envelope

I am puzzled by the first photo of the Mettler envelope without window C5 (500 pcs.), which seems to show the C5/6 format. Can you confirm that these are indeed normal C5 envelopes? Thank you very much.

Good day Does article "Mettler Couvert Fenster (C4, 120g/m², 250x)", art. no. 5607288 have window on left or according to description also window on right like art. no. 5607287?

Hello! 500 pieces ? Best regards