Look , here're two coins named Kai Yuan Tong Bao — the sort of coin made in memory of the founding of a new dynasty . These two coins were made in different periods of the Tang Dynasty .   How can you tell the difference ? From what I see , they look almost the same .   The one made in the early Tang period is bigger and has more characters on it , while the one with smaller and elegant characters was made in late Tang period . Look carefully , and tell me if you see the difference now . 