I wanted to confirm the translation. In order to do at least something productive for this thread, here's the (original) German text (and some thoughts - I hope nobody minds the digression)
"Bei T bleibt der Verschluss offen, bei B muss Finger auf Drücker gehalten werden, um Verschluss offen zu halten."
...and while the translations and the described handling of B and T settings is correct, and language sure has changed a bit (as has handwriting), the term "muss Finger auf Drücker gehalten werden" makes me smile, because it seems to tell a whole little story (as a historic document).
a) Whether it was written as a reminder, or as a note from the sender of the camera to the recipient, using the word "Drücker" (pusher) instead of "Auslöser" is somewhat cute. Either the writer or the recipient was probably not a versed photographer (the mere existence of the note seems to imply that already).
b) What kind of film was supposed to be shot and in what lighting conditions? Obviously there was an expectation that either B or T were going to be used at times (but not too often). Was there going to be a tripod/stand of sorts with the camera? How did they estimate or measure the exposure?
Sorry, if I went out of bounds here, but maybe I got a bit carried away to make use of my native language again... ;-)