
Not particularly rare but made of 22 carat gold. Because of the damaging solder mark on the reverse it is worth just the gold value - about £160 on todays prices.
That is not to say it is easy to get the full value for it - jewellers shops will offer considerably less as it is straight scrap for them and they need to make a margin (sometimes excessive!). Coin dealers will usually offer a bit more, but still need to leave a margin. A bullion investor is your best buyer - whether direct or through an online auction.