Coupler truck rivet that fits 41, 42, 51 and 56 Switchers as well as #53 Snowplow.
480-25T-090 Base Plate & Coupler Assembly w/Tab
This is a set of 6 plastic coupler knuckles w/spring and 6 knuckle rivets.
Plastic Coupler plunger armature assembly w/metal thumbtack used on several Lionel rolling stock.