Who is the designer BJ Dahlquist ( or Dahlqvist) and when did he design furniture?
Do you mean Bjarne Dahlqvist? He is Finnish inventor and entrepreneur, who has started the famous furniture factory BD Möbel: http://www.bdmobel.com/
We found no personal information about Bjarne Dahlqvist, but maybe you could ask directly from the company. Few months ago Finnish TV broadcasted a documentary about him. The documentary was called "Yrittaja Bjarne" and it was about him and his businesses in Estonia.