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you are correct about ship,s compass This is the compass from a Binnacle...that is used on a boat...we need to see a makers mark or serial number,..here are images of Binnacles...just to let you see what they look like,this part that you have, you can see the outer ring of the compass this would be mounted on the Binnacle,as this one is only 130mm in dia, then it would have been used on a small boat,http://www.google.co.uk/search?q=binnacle&hl=en&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=giqNUNzOFsGi0QWukYHQDw&sqi=2&ved=0CC4QsAQ&biw=1024&bih=675
I would advise against opening the compass,if there was a makers name,it would either be on the dial,or somewhere else on the external,brass work....
without a makers mark i could only hazard a guess,...and judging by the level of corrosion...maybe 100years....but then that would depend on where its been kept,??
the letter O.is used in German...e.g. Nord = North,..Sud = South,..West.= West, Ost,.= East,..Mitte,.= middle,...it may well be of German origin