Scripophily is the study and collection of stock and bond certificates. 
A specialized field of numismatics, scripophily is an area of collecting due to both the inherent beauty of some historical documents as well as the interesting historical context of each document.
Some stock certificates are excellent examples of engraving. Occasionally an old stock certificate will be found which still has value as a stock in a successor company.
Novelty notes and cheques have also been included in this category.