I'm no expert, but it looks almost identical to the Tour de France model from the 1950s - I have one of those for a Claud Butler rebuild I'm working on. Yours is a 5-speed one, and looks in excellent condition - I haven't seen a Spanish-made one before.
If you are interested in the history of the Simplex derailleur then Raymond Henry's "Fifty Years of Development of Simplex Derailleurs" is also in my Dropbox at https://www.dropbox.com/s/e8evpyy450pwsdd/simplex 50 years.pdf?dl=0
Raymond Henry, the author, supplied me with this copy.
Work within its limitations and you will be able to appreciate the best gearing on offer at that time.
Much appreciated - thank you. Those fitting instructions in particular will be invaluable (I like the idea of the wing nut for the shift lever to allow for changes in friction on-the-go), but the other document is also of interest.