On May 14, 4:59*am, al_main_at_hotmail_dot_...@foo.com (lindisfarne70)
> I recently discovered a vintage bottle of 25% proof 1970 Lindisfarne Mead
> from the back of the drinks cabinet. It states that there were only 7500
> bottles made and is individually numbered and signed by the maker. Its
> also 25% proof, which is far stronger than the 14% proof stuff available
> today.

If you are talking about US alcohol content, it is either 25 proof or
25% by volume, but only proof or % can be used with one number, since
US proof is twice the % alcohol by volume. It would take a super yeast
indeed to ferment to 25 % by volume, if at all possible, so this is
highly unlikely. Perhaps the mead is somewhat fortified. Proof has
been used in a different context in the UK in the past and is not the
same as US proof.

> As I've just saved this from being thrown out to clear space; does anybody
> know if this is worth something or should I just (attempt to) drink it
> assuming that it is still drinkable.

I have no idea how well this would have kept, but my guess is, that
like most beer, most mead would not last well for over 40 years and
would not now be worth much. However it is just possible that the mead
still is good, just as a very few strong beers are designed for aging
well. If you have the time, perhaps a Google search will turn up