In addition, I have seen a few old ports that have been recorked - usually in the UK. Some 1908 Cockburn's that had been recorked by a wine firm in the UK came up for auction several years ago, for example. The saving grace for many of the really old wines from the 1800s, especially vintage Madeira, is that they often were sealed with a heavy coat of sealing wax over the neck rather than using a lead foil. This wax seal can protect the wine long after the cork no longer can seal well, and the seal can be patched with more sealing wax if necessary. Of course many vintage Madeiras were kept in large glass demijohns for decades before sealing in a bottle, so the cork often is considerably younger than the wine inside the bottle.
My mailbox is always full to avoid spam. To contact me, erase snipped-for-privacy@webtv.net from my email address. Then add snipped-for-privacy@yahoo.com . I do not check this box every day, so post if you need a quick response.