<HTML>Hello Andrew !      Please excuse the late comment on your post.  The Action you describe sounds to me that it  may very well be a  Langer.  The first of the Langer  action of this type had no tension adjustments however the later models did have a screw type adjustment. This addition to the upright action was very successfull.  I think the small cost is why it is not used today.  I always stress in my classes that when a factory saves a quarter--- that  quarter is 100% profit.    In 1888  Siegfred Hansing  invented an upright action that was designed for the ultimate repetition.   It was very complicated and the cost of production would have beed very high.  And this does not address the labor cost to regulate. Regretably  I have never seen one of these actions, perhaps one day ---- soon.      I am begining to build a collection of  models of these types of actions.  I would guess there will be about six in total.   I will post the list on the progress of this effort.  Hope you find this helpfull, Regards to all, Jack Wyatt </HTML>