A wide range of commemorative coins are being struck - from the rare kilo coin to the £5 silver which will be more readily available.
The two arrived late after their helicopter was forced to make an emergency landing minutes after taking off from central London.
Tributes have been paid to Princess Lilian, both in Scandinavia and in Swansea where she was born, after her death at the age of 97.
Prince Charles has unveiled a plaque at the restored and renamed Redhouse Town Hall in Merthyr Tydfil.
He told onlookers he is "very impressed" with the building.
One lady in Merthyr asked Prince Charles for a "selfie" with her but he said it would ruin her reputation! http://t.co/9APRGwKihf
The Prince's visit has seen him visit some of Wales' most historic buildings and meet people from communities in Pembrokeshire, Carmarthenshire and Merthyr Tydfil.
The Prince of Wales has arrived in Merthyr Tydfil as part of his St David's Day visit to Wales.
Earlier today, he visited Llanelly House in Llanelli.
The Prince of Wales's nose proved an irresistible attraction to a toddler whose parents endured watching their home burn to the ground during the Tottenham riots.
Charles returned to the scene of the major disturbance to learn how the area is recovering.
The heir to the throne shared a lighter moment with husband and wife Mehmet and Burcin Akbasak - who lost their home when rioters set fire to the Carpetright building and flats above.
The dramatic pictures of the Tottenham landmark glowing red hot became a iconic image of the August 2011 riots.
In the shadow of the rebuilt building, Charles sympathised with Mr Akbasak and his wife - who are originally from Turkey - as the couple held their twin daughters Kayla and Lara aged 12 months.
Kayla reached out and made a grab for the prince's nose and he leant forward and happily let the toddler play with his face.Mr Akbasak, 33, said: "Both my daughters are friendly but Kayla was quite interested in the prince and they shared a nice moment."
Prince Charles has met with residents affected by the fierce flooding in Somerset.
The prince made his visit during a sunny spell, although another wave of bad weather is expected to hit the region between 3-pm today and 11pm tomorrow, according to Met Office forecasters.
The Prince will also talk to residents, farmers and business owners in Muchelney.
Prince Charles has been transported by boat to the cut-off village of Muchelney in Somerset.
The prince was then given a tour of the area on the back of a tractor, to see for himself what locals have had to deal with in the flood-hit region.
The Prince of Wales was meeting residents, farmers and business owners in his tour of Somerset.
The Prince of Wales and the Duchess of Cornwall survived an emergency helicopter landing last year, it has emerged.
Four other passengers were travelling on the Sikorsky S-76C helicopter on May 23 last year when the aircraft got into trouble, a report by the Air Accidents Investigation Branch (AAIB) said.
The heir to the throne and his wife were on their way to an engagement at the Hay-on-Wye festival in Wales, when the helicopter begin to veer - or yaw - to the right as it approached Denham aerodrome in Buckinghamshire.
The 53-year-old captain declared a Pan emergency, a less serious declaration than Mayday, and carried out a running landing at Denham.
It was described at the time by a royal source as "quite a hairy incident".
Prince Charles has been in South Wales today to celebrate anniversaries and achievements.
He started at the offices of the Abergavenny Chronicle meeting staff and celebrating the 125th anniversary of the Brecon and Radnor Express.
After then he visited Tredegar House to meet the mentors who have been helping the over fifties get back into work. He finished the day at the Ewenny Priory.
Megan Boot reports.