Anderson glazing bead
A contractor from Ft. Wayne, IN says:
April 15, 2016
This is the glazing bead on an Anderson 3-lite slider. It is for the center panel (picture or fixed) and goes with 3/8" glass. I don't know the age but I am assuming the 80's.
Tom from SWISCO responded:
April 18, 2016
It's hard to make out the glazing in your photo, but start with our 55-310. This is 3/8" Andersen window glazing. Could this be a match?