Hmmmm, 40 years is a bit optimistic on those plastic gears. My wife's 538 has been shedding plastic gear teeth since it was around 10 years old. And she bought it brand new. The problem is, she USES the machine. It's not just an underwear repair machine. She's made crafts, clothes, a vinal seat for my PU, a head liner for our Buick,
and only God knows what else.
Twer the gears steel, that would have never happened.
I agree on the Class 15 design. Right good work there.
Joe