This is a one piece design 80/63 transposing gear (change gear). This is a 3D plastic printed gear designed to fit the Heavy 10 double tumbler lathe. This should also work with the single tumbler, but I believe a bracket would need to be fabricated.
This combination of sizes (80/63) is commonly used for transposing the speeds on lathes with 8 TPI lead screws for cutting metric sized threads. While not truly perfect, the margin of error is .0125% or .0002" per foot.