I'll try to post a picture of the plaque shortly. Using the great resourses this web site provides, I have been able to match the letters on the plaque to
Hamburg Amerikanische Packetfahrt Actien Gesellschaft (HAPAG). This particular UBoat was apparently one on 113 built at Deutsche Werft AG in Hamberg.
By eliminating the ones that don't match the circumstances of this incident [whole crew lost,destroyed by aircraft, etc] I was able to narrow the possible names down to 6 U-Boats. The BUCH-No. 2570 still has me stumped.