Sterling Silver Devotional Metal Pendant with Guilloche Enamel

Vintage sterling silver devotional metal pendant. It has sky blue guilloche enamel.  It is 1 1/8" tall. Weight: 4.7 grams. It has a nice warm original patina. with some smooth wear. Marked sterling.  Very tarnished.I am puzzled by this one as it has the text regarding Mary, but the center is plain with no Mary. It has no evidence of ever having Mary attached as it is smooth and covered with enamel.