Not sure where people are getting 500% from.
Hmm.. maybe they get it from OP..?
"
staking at a rate of 500% thereafter"
Its clearly stated there.
It looks like the interest is 500%:
$ GoldPiecesd getmininginfo
[..]
"stakeinterest" : 500000000,
[..]
Not exactly sure how to parse the number of zeros, but 500% looks right if you remove 6 zeros like I've seen for at least one other POS coin.
I just got into GoldPieces a few days ago (for some reason the low-res logo and name really appeal to the nerd in me). Looking forward to seeing this coin integrated into some games!