I bought a Seiko LordMatic cal 5606A and noticed the quick change day-date wasn't working.
A bit of Googling found out that they rarely do on these movements, due to the plastic wheel on the day-date corrector wheel rocker breaking (see pic).
As it's such a common problem, I thought I was lucky to find a NOS one on ebay.
Unfortunately the plastic wheel on that was already broken - I've since read that this is common on NOS items, the plastic ages and breaks.
The one I have at the moment is spare time, so I found a bit of brass from an old pocket watch, got my finest file (#6),