Tender pick-up is the piece that contacts the track. The other two pieces would be the Spring and the Hair Pin Cotter. Each truck on the tender has one assembly. I believe they were for added pick-up. Mostly found on engines with the Air Chime Whistle. Your 21130 did not have that feature. Hope this helps. Similar to what you find on the diesel trucks.
Last edited by cramden; 04-17-2017 at 02:19 PM..
Reason: Add. info.