What a fantastic coin, Hans! It is one from the major leagues of numismatics (coin collecting). Old Spanish gold and silver coins played a giant role in the development of North, South, and Central America, and you can understand this even today by noting the close correlation between sizes and denominations of modern American coins and Spanish colonial coins.
Gold escudos and silver reales in 1/2, 1, 2, 4, and 8 unit denominations appear in American folklore with nicknames like gold dubloons and pieces of 8, and the denominations correspond roughly to our 5 cents, dime, quarter dollar, half dollar, and one dollar denominations even today.
You can add many of these coins to your collection for reasonable prices. Hans coin, a large, well-preserved gold coin authenticated, graded, and encapsulated by ANACS, a respected third-party numismatic service, will cost you a bundle.
These old beauties stand on their own merits, and values we can give on the CoinQuest forum are barely accurate due to the wide variations possible. In general:
worn: $1000 US dollars approximate value
average circulated: $3000
well preserved: $10000
The denomination (size) of the coin affects value strongly, but the most important factors are state of preservation, lack of damage, and eye appeal. Counterfeits, of which there are many, are worth zero. Consult a knowledgeable collector or professional coin dealer for an in-person appraisal.
The coins in our pictures are typical Spanish escudos from the era of Hans' coin. Robert Wilson Hoge has a superb article in the journal of the American Numismatic Society about Spanish colonial coins. Robert cites the main CoinQuest picture as coming from Mexico, Spanish King Philip V, gold 8 escudos ??'royal,� 1729/7, assayer R over D. (collection of the Hispanic Society of America) 35 mm in diameter.
The secondary picture (with shaded background) comes from respected Internet dealer Munzhandlung Ritter GmbH in Dusseldorf, Germany. Ritter is selling this (small) 1 escudo piece for about $2,500 US dollars, an excellent price for such a well preserved piece. From this price you can get an idea of value for well preserved Spanish escudos.
As always, with any valuable coin, you must be aware that conterfeits are everywhere. This is not a problem with Hans' coin, since it is certified by ANACS.
CoinQuest thanks the ANS and Ritter for use of their coin photos. They are beautiful specimens!