26.61 Grams. Cayon-2844 Calico-187
This coin is the first ever crown size coin and 8 Reales ever struck in Spain!!!
While the coin is dated 1474-1504 it was actually not minted during then. Sources disagree as the exact date range but all say within the time period of 1530's to the 1566 during Charles I reign. The Grandson of Ferdinand & Isabella, and the Holy Roman Emperor. 
What is known is that the coins of this style, still bearing Ferdinand & Isabella's names, were apparently struck through Charles I reign. This was politically sensible for Charles I, as his status as an Austrian outsider combined with Ferdinand's displeasure with him as successor to the throne threatened the stability of the (still relatively recently) unified Spain. Continuing to invoke the names of his respected grandparents, Ferdinand & Isabella, served to craft the impression of continuity within the Kingdom.
A book called Studies on John Hull, the Mint and the Economics of Massachusetts Coinage, by Louis Jordan briefly mentions these 8 Reales saying: 
"The first eight reales coins carried the inscription, shield and devices of Ferdinand and Isabella but it is now believed these undated coins were struck posthumously during the reigns of Charles I (1516-1555) and Philip II (1556-1598). The minting of these posthumous eight reales probably did not begin much earlier than the Cédula of Charles I of November 18, 1537 authorizing the Viceroy of New Spain to mint eight reales coins and they cannot be after the Pragmática of Philip II of November 23, 1566 which called for his own name to be used on future coins (Tomás Dasí, vol. 1, p. 49; Calbetó de Grau, vol. 2, p. 552; Gil Farrés, pp. 236-237 and Heiss, vol. 1, pp 161-162)."