Analysis of information sources in references of the Wikipedia article "500 (card game)" in English language version.
500 is known as the national card game of Australia. I took an informal poll and most (non immigrant) Australians will know of the game, even if they last played it at a school camp and are a bit vague now on the rules.
Open Misere is higher than Ten Diamonds but lower than Ten Hearts. You do not have to wait for the bidding to reach any particular level – Open Misere can be bid over any lower bid, or even as the first bid of the auction.
The Joker in no trumps: The most commonly accepted practice is that the joker can only be used as a trump card if the player holding the joker cannot follow a suit led
The Joker in no trumps: (...) However a player may use the joker to call it any suit and lead it at any time.
Any player changing the suit of any call he makes at any time gives all players the right to re-enter the bidding.
Strangely enough most players have been taught to call the joker, by calling six no trumps if you hold that card, and this regardless of any other strengths in that hand.
A key piece of information is the location of the Joker. It is common to bid six No-trumps if you hold the Joker.