I reckon this would probably be a good deal:
http://www.ebay.co.uk/itm/231401588597?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
Assuming he didn't break the balance when removing the back, it shouldn't be too expensive to get a service and a new crown.
@rodabod started
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I reckon this would probably be a good deal:
http://www.ebay.co.uk/itm/231401588597?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
Assuming he didn't break the balance when removing the back, it shouldn't be too expensive to get a service and a new crown.