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I am messing about with a Slavia 1601 (part of my work rescuing watches for local charity to sell on). The hairspring has broken at the collet. I sourced a new balance complete for a 1601 but it turns out it is for a Slavia 1600 (a Renata 5095). The main difference is that the 1600 has no shock system but the 1601 has. Everything else seems to be the same. I tried the new balance anyway but it does not work as the end shake is too high and disappears quickly if reduced. On checking I see that the length and shape of the pivots are different, which I suspected would be the case anyway (I checked the staff dimensions on line and all the rest appear to be the same). As this is an inexpensive movement I don't want to waste any more money on another balance complete, which are hard to get hold of anyway at a reasonable price. My thought now is to transfer the hairspring from the new to old. Both calibers have the same beat rate but the balance wheels are very different. The non-shock wheel is smaller in o/d but has peripheral screws fitted, whereas the shock balance is a simple 2 spoke wheel larger in o/d (the overall o/d's are the same for both). I acknowledge the implications of poise etc etc but is it likely that the non-shock wheel is heavier (I have no means to accurately weigh them) or has more rotational inertia and therefore has a stronger hairspring than the shock balance? How would the effects of a stronger hairspring manifest itself in the running of the escapement? Your comments would be appreciated before I mess about with a perfectly good new balance which I could resell if needs be.