Upgrading from NCS UNC details cleaned to NGC MS-64

One of the features I like about the Signature Series registry sets is the option to populate slots with NCS slabbed coins. Not that I want to fill my slots with these coins, but I sparingly fill slots with expensive coins that I can purchase for less. When I do populate slots with these coins, it is with an eye to upgrade them at a future date. From time to time I comb e-bay for these coins to see; 1. What prices are my coins bringing on e-bay and 2. Can I upgrade a coin I currently own inexpensively. The opportunity to upgrade came yesterday with a coin currently in my "Inspirational Ladies" Signature Series Set. The coin was a 1897 Netherlands 10 Gulden gold coin I originally purchased raw for $234. Since it was evident this coin was cleaned, I sent it to NCS and they returned it detail graded UNC cleaned. Yesterday I purchased an 1897 Netherlands 10 Gulden gold coin graded NGC MS-64 for $260! If an opportunity to upgrade comes for only $26.00, I'll snap it up every time. Since I had the NGC certification number from the e-bay listing, I immediately updated my set and will add photos when I receive the coin. Another advantage in upgrading is selling the old coin and minimizing the cost of the new coin. Rarely do opportunities come to upgrade this much for this little money. So when opportunity knocks do not delay, these opportunities are few and far in between!