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.

• 737bc01 Plate Special 2 x 4 with Train Coupler Open with Hook this part is a sub-part of it
• 737 Plate Special 2 x 4 with Train Coupler Closed for Hook this part is a mold of it
• 753 Plate Special 2 x 4 with Train Coupler, Open for Magnet [Reinforced] Mold of this part