I'm not all that familiar with the bust half dollar series, but does the date really look like this (and are off center strikes at all common)? http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250770914723
To give you the easy answer. Yes the date can look like that, and yes there are alot of die marriages in 1807 that do in fact have off center strikes. Look at a typical O-105 R1 for example. The coin has been cleaned harshly, but nothing makes me suspect it at first glance.
