The age of a grapevine can be estimated with 1-10% precision by dendrochronology (greek dendron=tree limb, khronos=time and logos=study), the scientific method of dating tree rings, using chemical staining and a microscope.
It has often been said that dendrochronology was impossible for grapevines, but this was recently proven wrong. I have recently learned the technique from a retired professor in Switzerland.
Core sample are drilled in situ using a professional Haglöf 10” 3-thread increment borer. The hole made at the base of the trunk of an old grapevine is 4.3mm in diameter, which is not harmful to the plant. Micro sections of the core are sliced with a microtome, stained with specific chemicals and observed under microscope. The age of the vine can be determined with a precision of +/- 1 to 10%, depending on the age and the morphology of the vine.