Complex sentence: The originally-planned hendecagon-shaped edge, which would have distinguished it from the quarter, had been abandoned and replaced with a depiction of an hendecagon and the same reeded edge as the quarter, thus compounding the confusion.
Split into simpler sentences: The originally-planned hendecagon-shaped edge, which would have distinguished it from the quarter, was abandoned. The hendecagon design was replaced with a depiction of an hendecagon and the same reeded edge as the quarter, thus compounding the confusion.