In Romans 1:1 and Philippians 1:1, the Apostle Paul refers to himself as a doulos Christou Iesou, which is translated "servant [or bondslave] of Christ Jesus."
The design in this section uses an uncial Greek font which is indicative of the time when the New Testament documents were actually written. Shorthand versions of holy names, called "Nomina Sacra" were employed in these manuscripts with lines on top of a two letter abbreviation. What looks like XY and IY is actually the genitive form of the Nominative Sacra of Christou Iesou or "Christ Jesus."
Be sure to also check out my other section that uses a standard Greek font.