After seeing this pic of the Martinair retrojet (B767 PH-MCL) I noticed a small window (hole) just left of the front maindeck door on the right side of the aircraft. (half in the read cheat-line).
A search in the database showed me that more boeing 767's they have a similar window/hole too.
Photo © Andreas Fietz
Photo © Alejandro Ruiz
Can anybody tell me what the purpose of this window/hole is?