The photomicrograph at left was made at 500X with a Nital etch near the core of the specimen, while the second photomicrograph was made of the high carbon case at the same magnification.
Cementite is smooth etching and usually looks slightly yellowish as well as having a distinct boundary around it, whereas proeutectoid ferrite is a flat (not glossy) off white light grey and is continuous with the ferrite in the adjoining pearlite.