Abstract: A manually releasable coupling device for connecting an elongate operator chain (2) with a frame or main frame member of a window comprises a first coupling member (3) for connection with a free end of the operator chain (2) and a second coupling member (6-10) designed for mounting in or on the frame or main frame member. The first coupling member is a flat disc-shaped element (3) with a substantially keyhole-shaped recess 85), while the second coupling member comprises a shaft section (6) for mounting in a bore in the frame member or the main frame member in connection with a turning handle (7). The shaft section (6) has a local constriction (8) for releasable engagement with the keyhole-shaped recess (5) in the disc-shaped element (3).In order to allow manual closing of the window under surmounting of sealing pressure, the shaft section may be eccentric relative to the rotational axis of the turning handle.