I love them. Had an old bottle, 9kg ( it was actually in pounds ) apparently the old man reckoned it was leaking. After an hour the only test date I thought i could find was maybe late 60's, couldn't be sure. Cleaned it up, got home from work around midnight, had a beer and headed to the servo. Old mate was near asleep at 1 am, didn't really want to be out in the frost, and swapped it without a worry. I'm sure it became an Oz pig or similar.