Difference between Graybeard and Methuselah

What is the difference between Graybeard and Methuselah?

Graybeard as a noun is alternative spelling of greybeard. while Methuselah as a noun is a wine bottle having the capacity of eight standard bottles (six litres)

We hope you now know whether to use Graybeard or Methuselah in your sentence.