About agitator colors
The Roto-Swirl changed from bakelite to polypropylene (and thus from a drive-block arrangement to a splined drive link) in 1967. The first poly Roto-Swirls were black, but not for long.
In 1968 the Straight-Vane was re-engineered, not only to make it a 'propylene agitator as well, but to re-contour the vanes in shape. When the new version debuted, it came out in gold. The Roto-Swirl was changed to gold at the same time, thus we only had black splined, propylene Roto-Swirls for one year or so.
The Roto-Flex had been made from Polypropylene from 1965 onward, also in gold but it was speckle flaked material, which was pretty high-tech for 1960s plastics technology.
To my knowledge there was never a black Vari-Flex.
According to when this machine was produced, if the Roto-Swirl is its correct agitator, it could have started in 1966 with a bakelite RS, then produced in 1967 with a black plastic RS, then in 1968 with the gold version. Running changes to parts such as this always impacted ongoing models with slight variations (and thus minor changes the the model number as well).
Gordon