Angus,
Either all the Brewsters aren't alike or I have one that is something else too. Two of mine have the long spring that fastens to the upright piece, one has a spring that goes kind of wraps around the pivot and bent ends that fasten to either end to make the action. Sorry if that is hazy but if necessary I can take a picture. I notice all of the ones I have have some differences in the yoke that contacts the shell. I didn't know if it was factory or something fashioned by a previous owner. I have 2 variations of the adjuster for the length of stroke as well. Two are a bent wire and one is a plate. It is very easy to let the aluminum finger or yoke get into the knurled nut that holds the shellplate if you cycle it without a shell in place to index. That works kind of like a file on the end of the yoke. Ask me how I know.
RS
