It can't be a 1911 Victoria coin because she died in 1901.
"dei gra" isn't the denomination, either; it's part of a motto that appears on all British Coins.
Please post a new question with the coin's denomination and date. If you can't find the denomination, describe the image on the side of the coin that's opposite to the portrait of the king or queen.
Check your coin again. Queen Victoria died in 1901.
King George V wasn't on any coins until 1911.
No, it is not an unusual inscription. It is a variant of the same thing, but it is unusual on a Threepence. The smaller coins do not have the full inscription due to limitations of space. The phrase "VICTORIA DEI GRA BRITT REGINA FID DEF IND IMP" is mostly abbreviated from Latin. The literal definition is - "Victoria by the Grace of God, Queen of the British territories, Defender of the Faith, Empress of India".
There were no Australian (or Western Australian) Pennies minted prior to 1911. An image of Queen Victoria and the inscription VICTORIA DEI GRA BRITT REGINA FID DEF IND IMP (Queen Victoria, by the Grace of God, Queen of the British Territories, Defender of the Faith, Empress of India) or similar, would have appeared on the obverse of any official British coin minted in 1896. What you may have is a Traders token or a medallion. The reverse may have a business name and address on it or, some sort of commemorative inscription.
George V coins were issued from 1911 to 1936 inclusive.
The Florin was reintroduced into the British currency in 1848 as one tenth of a Pound (or Two Shillings), as a tentative step towards decimalisation. The usual inscription on British coins at this time was similar to this - VICTORIA DEI GRA BRITT REGINA FID DEF. This is Latin and the literal definition is - "Victoria by the Grace of God, Queen of the British territories, Defender of the Faith". The "godless" Florins were so called because the reference to god (DEI GRATIA, DEI GRA or D G) was omitted from the Florins. There was a great furore about it, and in 1851, D G was included on the Florins.
IND IMP was part of a much larger title used by British Monarchs. It is abbreviated Latin and means Emperor (or Empress) of India. IND IMP (India Imperator) was used on British and British Empire/Commonwealth coins from about 1893 when India became part of the British Empire, until 1948 when India became independent. Depending on who was king or queen at the time and which particular coin it appeared on, the legend may have appeared as - "VICTORIA DEI GRA BRITT REGINA FID DEF IND IMP" "EDWARDVS VII DEI GRA BRITT OMN REX FID DEF IND IMP" "GEORGVS V DEI GRA BRITT OMN REX FID DEF IND IMP" "GEORGVS VI DEI GRA BRITT OMN REX FID DEF IND IMP"
Such a coin does not exist. Queen Victoria died in 1901. The legend "Victoria-dei-gra-britt-regina-fid-def-ind-imp" does not help identify a coin. It could appear on any British or British Empire coin issued from 1838 to 1901. You need to describe the design on the coin, the metal it appears to be made from and the diameter. Coins dated 1951 would have George VI on them. If you do indeed have a Queen Victoria "coin" with 1951 on it, it may well be a souvenir token commemorating the 50th anniversary of her death.
Queen Victoria ruled the British Empire from 1837 until her death in 1901. The legend "VICTORIA DEI GRA BRITT REGINA FID DEF IND IMP" is mostly abbreviated from Latin. The literal definition is - "Victoria by the Grace of God, Queen of the British territories, Defender of the Faith, Empress of India". This expression and variations of it appear on the obverse of all pre-decimal coins of most British Empire/Commonwealth countries. The 1899 British Penny is not rare, there were over 26 million minted.
The legend DEI GRA REG FID DEF is abbreviated Latin and has appeared on British coins and many coins of the various Commonwealth countries in one form or another for many years. The phrase "VICTORIA DEI GRA BRITT REGINA FID DEF IND IMP" is mostly abbreviated from Latin. The literal definition is - "Victoria by the Grace of God, Queen of the British territories, Defender of the Faith, Empress of India". The equivalent phrase for Queen Victoria's successor, King Edward VII, is - "EDWARDVS VII DEI GRA BRITT OMN REX FID DEF IND IMP". The literal definition is - "Edward VII by the Grace of God, King of all the British territories, Defender of the Faith, Emperor of India". The phrase varies as the Monarch and the gender of the Monarch changes, and as the circumstances of the British Empire/Commonwealth changes. The expression does not describe the coin, but is part of the many titles of the king or queen, whoever he or she may be at the time.
Regina is Latin for Queen. Depending on the year of your coin, it could be either Queen Victoria (1837 to 1901) or Queen Elizabeth II (1953 to present). DG or DEI GRA is abbreviated Latin for Dei Gratia - meaning, by the Grace of God.
I imagine this to be a coin set in a mount on a ring, but the description is incomplete. If it is a coin it is probably a sovereign. Modified coins have no collector value.