That's the contact info attached when I bought a replacement gas spring in 2011:

DUNCO Apparatebau GmbH&Co.KG
Innungsstr. 60
13509 Berlin
Fon +49(0)30/414 28 22
Fax +49(0)30/411 54 81
www.dunco.de
bestellung@dunco.de

The emails came from info@dunco.de

HTH.