This is one of my antique brass tools that I use to decorate my books. It is a monogram of the name of Jesus Christ. “IHS” is the Christogram for the Greek spelling of Jesus (ΙΗΣ- iota-eta-sigma; short for ΙΗΣΟΥΣ). Basically it is the first three letters of the Greek spelling. This is a very basic explanation of a very complex, and rather interesting history of the use of monograms in the early and medieval Church.