These stained glass windows are believed to come from the "old" church. These beautiful windows are on either side of the sanctuary, facing the east and west sides of the church; not visible unless you are near the altar.
If you are facing the altar, the window to your left (East) is King David. He is holding a harp or a lyre that indicates his connection the the Psalms.
The one on the right (West) is Mechizedek, the King of Salem. After Abram had defeated an enemy king in battle, he was met by Melchizedek who offered him bread and wine. He then blessed Abram, and Abram, in return, offered God a tenth of all he possessed.
In the Psalms we come across the phrase, "You are a priest forever, according to the order of Mechizedek." Newer translations might say, "in the line of Melchizedek." It is often used in reference to the priesthood in the Church, although there is no such thing as an "order of Melchizedek."