There are many reasons why the 8 escudos on the name of Philip IV from Madrid are so scarce.
A huge amount of silver was obtained from America at that time, but not as much gold was collected.
The silver and the gold obtained from America was mainly minted in America and not in current Spain.
The coins minted in Spain were useful for daily life transactions. In fact, most of the coins issued at that time in the Spanish mints were billion and small silver coins.
Most of the few gold coins that were minted in Spain at that time were minted in Sevilla. The reason is that Sevilla was the city were the goods from America firstly arrived.
Big gold coins would promote the exportation of gold from Spain to other countries, and this is something that no State would like to happen at that time. In fact, Spanish 2 escudo coins were much more common than Spanish 8 escudo coins.
Most of the few coins minted were later on melted.
Even if they are very rare, 8 escudos from Madrid are not as demanded in the international market as the ones minted in Mexico or other American mints. The reason is that American collectors consider the coins from the Spanish colonies as theirs, but they do not feel the same from the coins minted in current Spain. However, it is also true that more and more international collectors are discovering these golden beauties.
1635. Felipe IV. (Madrid). M. 8 escudos. (Cal. 8) (Cal.Onza falta, sólo publica este año con la ceca vertical) (Tauler 9a, mismo ejemplar). 27,01 g. Muy bella. Precioso color. Ex Áureo Selección 2007, nº 149. Rarísima. ¿Única conocida?. EBC.