Many classic Spanish stamps have serial numbers on the back. The Perfins Club might be able to help you. There is also a book on Spanish perfins listed on their website you could try to find. I also find a world perfins book on Abe Books: The Perfins of the World : A Catalog/Album
srdcruz and all - - It was common practice for Spain and the colonies to have 'accounting' or control numbers on the backs of their stamps. The perfin BHA was used by Banco Hispano Americano and was based in Madrid. Hope this helps? Chimo Bujutsu
Thank you so much
