A detection device detects a thickness anomoly region within a strip of stock and includes a first roller operatively rotating as the strip of stock passes over a first roller surface; a pivotally mounted pinch roller positioned to operatively pivot about a pivot axis against the strip of stock passing over the first roller; a photoeye mask positioned to rotate about the pivot axis responsive to pivotal movement of the pinch roller; a photoeye slot within the photoeye mask extending between a slot leading end and a slot trailing end; and the transmitting and receiving optical devices positioned on opposite sides of the photoeye slot of the photoeye mask and operative in an photoeye mask-aligned position to project a centered through-beam through the photoeye slot between the transmitting and receiving optical devices. The through-beam is blocked by the photoeye mask as the photoeye mask operatively rotates a preset deflection angle in either direction out of the photoeye mask-aligned position and into a photoeye mask blocking position. first and second directions. The duration of the disruption of signal between the optical transmitting device and the receiving device indicates whether the anomaly encountered within the strip of stock is a splice or a stock-out occurrence.