Variants of a mold are catalogued separately, so each one has its own sets and minifigs. Check these too if something you expect is missing here.

• 823c01 Garage Door, Glass - Old (with Counterweights) this part is a sub-part of it
• 823apr0001 Garage Door Glass (without Counterweights) - Old with Yellow Frame Print, without Hinge Pins this part is a pair of it