When I go to look at a vintage sewing machine I carry 2 screwdrivers with me. Usually if the dials in the front ( width & length adjustments ) are plastic; the gears are plastic. I always unscrew the top of the machine and look at the gears. Many good Singers were made in the late 60's & 70's. These machines do not have any plastic parts in them. Believe it or not people don' mind you doing this. They usually look at these machines as ancient while not realizing what gems they have. I hope this helps.