For me this excersize makes sense: apparently somewhere in Danmark there is an old chain with an interesting (hi)story, maybe one day when visiting Danmark I will find it. Also, I learned the word 'kæde'. According to Den Danske Ordbog it has the HIS(tory): 'over middelnedertysk kede fra latin catena'. As a student in Leiden I have good memories about the old students club Catena, which connected students from all disciplines and from all parts of the country.
So what is the word for "old" in Danish? The sentence makes much more sense if it is simply "the chain is old and brown". Given how cack-handed many of duolingo's previous English translations have been, I don't have a lot of confidence that what is being said in Danish is actually what is being conveyed to an English speaker.