Buying the old coin is not worth anymore except the popular old coins like doge, litecoin or something else and why? this project already lost interest from the investors and traders.
https://coinmarketcap.com/currencies/primecoin/markets/

It's almost die right now. It's only worth to bet into the pump that no one knows when that will be coming for sure.
It's only wasting our time to buy the old coin while we can make money from the new coins easily dude.