The VCNT2020 from Vishay is a reflective sensor in a miniature SMD package. It has a compact construction where the emitting light source and the detector are arranged in the same plane.
Confirmed by manufacturer, there is no top mark to show orientation. The detector side pads are wider than the emitter side pads. This is the only way to judge orientation.
Applicable part numbers
VCNT2020TR-ND
VCNT2020CT-ND
VCNT2020DKR-ND