A British 2012 22 carat gold Quarter-Sovereign coin (Elizabeth II),(boxed Proof) is currently retailing for £130 GBP from the Royal Mint.
According to the PCGS Price Guide, which is available free online, Its value is $900.00.
The current value if $49. ----- The price varies according to the market. As of 2012-07-25, PCGS lists it as: 1956 Proof Set: $57
PCGS does have this information on their web site. Or you can check Heritage Auction web site (HA.com) for previous sales of PCGS coins of this type.
August 10, 2009 The 1923-D Saint-Gaudens Double Eagle in MS66 grade has a PCGS value of $4,100.
August 25, 2017. $190 to $191.
Retail value is $29.00 for a set in original packaging, if any of the coins have carbon spots or ugly toning it's value drops ----- The price varies according to the market. As of 2012-07-25, PCGS lists it as: 1957 Proof Set: $32
August 25, 2017. $480 to $485.
The PCGS is the Professional Coin Grading Service. PCGS pricing guides can be found online on the PSGC website as well as sites like Coinnews and Davidhall.
The price varies according to the market. As of 2012-07-25, PCGS lists it as: 1956 Proof Set: $57
Nice uncirculated ones sell in the $300 to $400 range, but they need to be certified by PCGS or NGC.
As of 11/2008, about $440 for an uncirculated coin and $1060 for a proof version. Source: PCGS
Between $350 and $570 depending on condition. My advice would be to spend about $40 and have the coin certified by one of the big agencies such as PNG or PCGS, due to its potential value.