Two green ones! What luck, I am envious.
The rubber pulley can often be sanded down to even out the flat spot, which is very easy by just holding a sanding paper next to the pulley while the motor runs. It took me a few rounds of cleaning and oiling before mine was back to it's former self. I had the base off, and loads of fluff and dust had somehow gathered in the main body part; I used the vacuum cleaner to get it out. I take out the bobbin case more easily now, the first time I thought it might be very risky, but it really wasn't. The brownish staining isn't smoking or nicotine, it's decades of grime and old sewing machine oil and it comes off completely. I have shined up mine with car polish.