My dad's got one - the 5-speed model - bought in the late seventies and still quite original. I don't think his has SR cranks, but I might be mistaken.
It's not a bad bike - plain gauge 531 weighs a fair bit more than the butted version, but it's quite nicely put together and finished for what was a mid-range bike of the time.
would it be worth spending any money on or should just touch it up and leave it at that?
It's probably not one to spend a lot of money on to bring back to concours
condition, but it should make a decent runabout, commuter, hack, fixie...
If yours has the original Weinmann brakes, they often have a date stamp on the rear.
Calmes dans le demi-jour
Que les branches hautes font,
Pénétrons bien notre amour
De ce silence profond.