Silverline aluminum patio door.
A quick learner from Minneapolis, MN says:
June 2, 2016
Do you have any idea when Silver Line started making the 5100 aluminium patio door?
Paul from SWISCO responded:
June 3, 2016
Good question! I would say the early 1980's, which is when Silverline manufactured the aluminum thermal brake patio door Series 5100.