Encyclopedia of Bridge(7th Edition) 150ページより。
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BEER CARD.
The

7 under certain special circumstances.
If declarer wins trick 13 with the

7 in
a successful contract, he claims,“Beer Card!”
and his partner must buy him a beer.
You cannot claim “Beer Card!” if you go down.
If a defender wins the last trick with the

7
and declarer has been set, the defender may
also claim, “Beer Card!” and his partner
must buy him a beer.
A defender cannot claim “Beer Card!”
if declarer makes his contract.
Greg Morse, with help from Jeff Goldsmith and
Sheri Winestock, unearthed the Beer Card history.
The

7 has a special role in a Danish game
called “Boma−Loma.” Partly because of this,
bridge players in Copenhagen were the first
bridge players to use the Beer Card term.
It became common in Europe and reached London
by the Eighties. The term was imported into
North America by the American Junior team after
they made a visit to Poland for a Junior Bridge
Camp during the Nineties.
It has since spread around the world, mostly
via World Junior Championship.
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という訳で、
「

7=Beer Card」は、ブリッジプレーヤーとして知っておくべきこと、のようだ。
少なくとも、本ブログの読者におかれましては、ぜひ知っておいて欲しいと思います。
なにしろ、ACBL発行のエンサイクロペディアに載っているのだから。(笑)