No regular shilling coins were issued dated 1919. This was an experimental piece produced as part of a planned debasement of the silver alloy (0.625 silver). The debasement, in the end, did not occur.
A similar pattern florin was struck in 1920.
According to The Australian Coin Chart 1966 "A few Pattern Shillings dated 1919 and 1937 have been reported and would realise over £500 at Auction". Greg McDonald's "Australian Coins and Banknotes" catalogue calls this an "un-issued circulation strike".
The "Renniks Australian Coins and Banknote Values" catalogue (Pocket Edition 1986) says: "Only two specimens are known to exist. One in Science Museum Victoria and specimen sold ex Spinks [1981, for $40,000]. The two known coins have been punched in the field of the coin with two small S's on the obverse and reverse to officially denote that they are specimens and to distinguish them from the currency issue. None were issued for circulation."
It has to be noted though that the specimen in the photo belonging to Museums Victoria (ex Science Museum Victoria) does not have said S punch marks.
According to Remick's "Catalogue of British Commonwealth Coins 1649-1971", 4 specimens are known. Krause 1988 Edition lists 6 pieces, later editions show mintage as unknown. | 
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