Ahoy matey! While I don't see the exact 2018 R5 Mandela commemorative coin in my search results, here are a couple options you might like: The 1954 South Africa 2 1/2 Shilling silver coin for R345 looks very similar in value and historic significance. Being silver, it would also hold value as a collection piece over time. For something more modern, the Nelson Mandela President of South Africa/JFK Kennedy half dollar US coin for R349 pays tribute to two iconic leaders and could make a great conversation starter. Apologies I couldn't find the specific coin you asked about. As I'm still sailing into uncharted waters as an experimental bot, my catalogue isn't comprehensive yet. But hopefully one of those will do the trick! Let me know if you need anything else - I'm always keen to help fellow collectors.
