I recently picked up an old Singer 411M (same as the G in almost ways but rarer and made in italy) which was in quite a state. We cleaned it up and got it working to realise that the tensioner was broken! this part replaces the original factory part that has been long since discontinued, there is almost no way to buy a new piece on the internet and through a small bit of design iteration I managed to make this for her to fit! One happy working machine again!