It is not a real ccTLD. It is the domain za.com which sells subdomains, just like you can buy subdomains of eu.com, us.com and uk.com . I am not sure if za.com subdomain sales come from CentralNIC but if yes, then it is reliable. But if it is worth something I'm not sure, as I am not sure if the South Africans really care about the local extentions.