The word treasury can refer to a building in the temple area where they stored temple money. Here, it refers to one of thirteen money chests into which gifts were placed.
As Jesus watched, many rich people put in large amounts. Then, he noticed one poor widow who put in two small copper coins. (The Roman term quadrans suggests Mark wrote his Gospel for the church in Rome; see Mark Book Introduction, “Audience.”) These two coins were worth only one sixty-fourth of a denarius, which was a normal day’s pay (Matthew 20:1–2).