1836-O 4-D comes from the French Connection family which has 8 documented varieties. All varieties from this family sport the New Orleans mintmark, and were likely produced in this vicinity although Riddell didn't document this variety in his 1845 Monograph. Apparently all of the examples I've studied from this variety were struck on billon planchets, but I'm pretty sure this one (and others I have photo's of) were struck on brass planchets!
 
This example has certainly seen many better days! However, I've never been able to offer any of the New Orleans mintmarked varieties before, and you probably won't find a less expensive example of this variety!