Troybuilt Econohorse tiller

[bluetrac]

I received a hand me down tiller from my dad, it is a EconoHorse with a 6.5 Tecumseh engine. I am doing the routine maint. and have come to the belts. Why does this unit have 2 drive (forward) belt pulley's? Also the sn is E0046923, any idea of the year model?

Thanks for any help in advance