Just picked up my 1985, 6309-7290 Slim Turtle from my watchmaker after a full service. New mineral crystal, and Vintage Time Australia seals installed. Never had a German datewheel, so that's pretty cool.
Not sure how to set the day/date? My Dad gave me this one awhile back. 😎
Not had one for a while but it usually goes like this.
1 unscrew the crown,
2 pull out 2 clicks,
3 change the time to 6.30 to avoid damaging the gearing (if you quick set around 8pm to 4am the mechanism might already be 'in gear' to change the date and get damaged)
You can skip 3 if you know you're not in the danger zone.
4 Push the crown down to the first click (it's quite a small difference)
5 Rotate one way to advance the day, the other way to advance the date (can't remember which way is which).