Old vinyl double tilt-sash window. Only marking is stamped into the metal balance channel shown below. Two imprints read 26B cBSI Pivots are broken off where they extend from the bottom channel of the sash. They normally slip into the bottom shoe, allowing the sash to tilt back into place. The broken grey pivot fits snuggly into a black plastic holder, and the assembled pair attaches in the bottom channel of the sash. The pivot can be adjusted by loosening a set screw.
Photos in order show 1) the broken grey plastic pivot (taped together) in its holder lying on top of a functioning fully assembled sash. 2) The broken pivot showing how it attaches into the bottom sash channel, lying on top of the good sash. 3) The stamped marking on the balance channel in its place in the window frame.
If I can repair the sash pivots, I will also want to replace the balances.