There are two types:
1. Designed by Oban Studios (in many different colours) and first issued in 1978.
2. Designed by Colin Terris for the Royal Mint in 2001.
Now your weight is inscribed R ##782 (not Rhh: unlimited weights are signed by a character, identifying the year of manufacture, plus a running number). R stands for 1997 - so it cannot be the Colin Terris one.
Best regards - Wolf