The C70 use:
M12 x 1.5 thread,
60 degree taper seat,
The original Volvo nuts have a 28mm diameter floating washer and a thin stainless steel cap that is the 19mm head. The issue with this is that these caps are easily damaged and often come off leaving a non standard size head which can be difficult to remove.
Spot On Nuts and Bolts offer these compatible replacement alloy wheel nuts to fit the original Volvo C70 alloy wheels.