✅ What exactly is this part?

👉 2104-1020 = Swing Motor Planet Gear

In other words:
➡️ A planetary gear located inside the swing gearbox (slewing reducer)
➡️ A component of the system that allows the excavator to rotate left and right

This part is clearly referred to as a “swing motor planetary gear”
It is used in Doosan / Daewoo Solar series machines

Technical example:

• Number of teeth: 29T
• Size: approximately Ø95 mm