Like already said, but maybe not necessarily a door post. Could have been worn around shoulder. Probably not forehead (those are usually black boxes). Hasidic Jews wear them on shoulder or head. They contain 10 commandments. Term Teffilin comes from Teffilah, which is the Hebrew word for Prayer. Practice comes from Deuteronomy 6:4-9. That passage is known as the Great Shema, Shema being the imperatival form of the Hebrew word "to hear" - command to hear that the Lord God is one.
Just a little further info on your find there...