"Pressure Barrel"...Anyone used one of these?

This is a hand-me-down from my brother in law, who was brewing back in the laste 90s. Has anyone seen, or used one of these before?

A few things to note about it:
-A 12oz CO2 cartridge can be screwed into the lid, in order to keep pressure.
-inside there is a tube from the valve to a floatation device that allows the valve to draw from the top of the beer at all times.
-The underside of the lid has a few #s, and "1987" off by itself. Not sure if this is just a random code, or a production date.
-I've looked for these online, and the closest thing I found was a brief mention of one on a British brewing forum.
-The LHBS owner said he had only seen one once in his life, and it was owned by a guy who just came to the states from Belgium.
-I haven't measured it yet, but standing it beside a fermentation bucket, its got to be around 5 gallons.
-The lid screws on and has a very thick o-ring to seal it. Suprisingly, the o-ring is still soft, and in good condition.

So....should I try it? I hate to loose 5 gallons if it doesn't work, but I can't spend the rest of my life curious about it. Also, my plan is to ferment in a bucket, then rack to this with some priming sugar....do you think I need to immediately hit it with CO2? I'm not sure there is a check valve that would prevent pressure from escaping when a cartridge isn't screwed in. LHBS guy says he thinks if I can keep pressure in it, it should keep beer for a couple of months...thoughts on that estimate? My wife is worried about BPA. I assume there is no chance that this thing is even remotely BPA free.

Thinking about doing 5 gallons of a cheap pale ale or something just to try it out.

There was a thread a few weeks ago talking about a european starter kit that is based around these tanks. It was the first time I had ever heard of them. You might find that thread if you search titles for "starter kit".

Every once and awhile we get questions about them from English Homebrewers, and I'm the only one that seems to seem to know what they are. I usually refer them to the English and Aussie homebrewer sites. None of the threads on here really go beyond 3-4 posts, because since the majority of us are from the states, where they're rare, we don't know much about them.

The best info I've found about them is just through Google. Search for UK pressure Barrel fermenter.