Can somebody explain these Caliber parts?
 

Hi,

Can somebody please provide some insight to these Kyosho Caliber parts?

I understand the part pictured on the left is the insert for the main gear, but the part
pictured left is different..

Does anybody have any clue ?

Thank you

Originally the caliber 60 came with the gear permanently fixed to the boss. Then if you chipped a tooth you had to throw it out.
The new design then was made two piece.

Insight appreciated! Thanks!