Other painting information given at the same time is.
All early R - Z - U - GT had black starters, black generators, and black
carburetors. U - GT had black oil filters.
The only reason we know is first assembly line tractore had no stater
or generators and were added later. The
black paint on the oil filters was a wrinkle finish type of paint that
oil would not attack. Later all factory installed
starters and generators were Praire Gold paint like the rest of the
tractor. No late model R,Z,ZA,ZB,U had black
starters or generators, carburetors, and oil filters.