Is there any value to postcards from Havana Cuba dated 1947?
Yes these have great value because of the STRICT no trade policy with Cuba
You should check on eBay for their value.
I think that you have either the date or the denomination of your coin incorrect. Your coin is from Spain, but the only coin dated 1947 was the 1 peseta ("UNA PESETA"). There was, however, a Fifty Peseta ("50 PTAS") dated 1957. The coin was actually produced between 1958 and 1975 (two digit year of production is incused in small numbers in the star on the back of the coin, to the left of the…
If such a coin existed it would be worth thousands, except that all 1947 cents were struck in bronze. They're only worth a few cents in average condition. Your coin should not stick to a magnet. With the exception of a few 1944-dated errors, the only steel cents were struck in 1943 when copper was needed for the war effort.