What plastic? The machine is totally all metal, inside and out - well apart from the knob on the stitch length regulator that your supposed to twirl to lock it at the stitch length you want. The bobbins are metal and it is a front loading bobbin - I always think they stitch better than the top loading ones you get a lot today. Even the original light bulb is still working - and the duplicate one I got off ebay for spare parts is exactly the same and all working beautifully.
The cams are some sort of plastic I think - but it is not hard plastic, a bit bendable and they work brilliantly. The only hard plastic thing that has got cracks is the top of the accessory box that sits along side the free arm when it's in it's case - the same thing has happened to the one I got off ebay.
Once I figure out how to post phots I will post them.