As to the dates, yes, I am confused as well and I must be mistaken.
This is the record I found on Ancestry.com:
Martin Valentine Tjaden, born in Norden (Ostfriesland) and living in Aurich (Ostfriesland)
I can't read the first word in the 2nd line, but the date looks like his birth date. Then Dec 23, 1859, (Captain) Koster, on the ship Schwann (to) England
I also found another record, but my German is almost nothing. His name appears in a directory of sailors traveling under the Bremen flag. The rest I cannot read.
His name is listed here and the ship's name is Schwan under Captain Koster:
The ship I found that had been constructed in Danzig in 1863 by Klawitter is probably the wrong Schwann. My mistake!! Sorry.
Now looking for a German ship, Schwann, built before 1859!!!