While the following are not directly on point nor comprehensive as to the 
original query, they provide varying discussions of Catholic medallions and 
related folk religion and popular culture variants.

Cheers,
Chris

****  

Bury, Shirley. 1991. Jewellery 1789-1910: The International Era. Woodbridge, 
UK: Antique Collectors' Club. 

Deagan, Kathleen A. 2002. Artifacts of the Spanish Colonies of Florida and the 
Caribbean, 1500-1800. Vol. 2, Portable Personal Possessions. Washington, 
D.C.: Smithsonian Institution Press. 

Elworthy, Frederick T. 1895. The Evil Eye: An Account of This Ancient and 
Widespread Superstition. London: John Murray. 

Elworthy, Frederick T. 1900. Horns of Honour and Other Studies in the By-
Ways of Archaeology. London: John Murray. 

Fales, Martha G. 1995. Jewelry in America, 1600-1900. Woodbridge, UK: 
Antique Collectors' Club. 

Hansmann, Liselotte, and Lenz Kriss-Rettenbeck. 1966. Amulett und Talisman: 
Erscheinungsform und Geschichte. Munich: Callwey. 

Hildburgh, W. L. 1906. "Notes on Spanish Amulets." Folklore 17 (4): 454-71. 

Hinks, Peter. 1975. Nineteenth Century Jewellery. London: Faber and Faber. 

Lightbrown, Ronald W. 1992. Mediaeval European Jewellery. London: Trustees 
of the Victoria and Albert Museum. 

Moss, Leonard W., and Stephen C. Cappannari. 1976. "Mal'occio, Ayin ha ra, 
Oculus fascinus, Judenblick: The Evil Eye Hovers Above." In The Evil Eye, 
edited by Clarence Maloney, 1-15. New York: Columbia University Press. 

Stafford, Thomas A. 1942. Christian Symbolism in the Evangelical Churches. 
New York: Abingdon-Chokesbury Press. 

Tait, Hugh, ed. 1986. Jewelry: 7000 Years. New York: Harry N. Abrams. 

Webber, F. R. 1971. Church Symbolism: An Explanation of the More Important 
Symbols of the Old Testament and New Testament, the Primitive, the 
Medieval, and the Modern Church. Detroit, Mich.: Gale Research. 

Winston, Anne. 1993. "Tracing the Origins of the Rosary: German Vernacular 
Texts." Speculum 68 (3): 619-36.