It is handmade by german frame builder Hugo Rickert of Dortmund. Due to a stroke he suffered some years ago he does not build anymore. It is a very rare an valuable bike, especially in this state. Rickerts a herdly seen on ebay and itf they catch high prices with collectors. They are verx sought after in the U.S. as far as I know since Hugo Rickert is one of the most famous german builders and he equipped the german national teams (Track mostly) for some time nad therefore had connections to some US riders.
As being a later (late 80ies?) model this might not be the most desireable model but still a beautiful bike. Just like you I would try to get it for a good price (Probably around 500 $ but not more) and keep it or let mum ride it. You just should care for maintenance since for mom it is probably just a nice riding bike.....
I wish you luck....
Those are the finds I am dreaming of....