Very Nice coin. It's listed as an R-5 in the 4th Edition Overton Variety book, however on this link which discuss's Bust Half Dollar Rarity Ratings the O-120 is listed as an R-3 with sub varieties (120a, unlisted) as being one Rarity Rating higher thus making a O-120A an R-4.
http://www.busthalfprices.com/ptrr.php
They're all hard to find in this beautiful condition.
http://www.busthalfprices.com/ptrr.php
They're all hard to find in this beautiful condition.





















