The outline of the inner portrait oval is often relatively smooth.

The outline of the inner portrait oval is often relatively jagged when compared to the Type III.

This is a relative distinction and must be considered along with other factors before making a determination. Many Type IIIs have somewhat jagged inner portrait oval lines and could be confused with the Type IV.

All the Type III examples are from the same scanned stamp from plate number 146, and all the Type IV examples are from the same scanned stamp from plate number 762.