Yeah...never seen any Casascius 2011 with print that dark. I have seen pics of a few 100 bars and none looked that dark.
I agree. The owner of this says he got them all from Casascius in 2011, and did a copy/paste of the 'receipt' email. I dont think there is anything going on here, but can never be too careful with a 100 BTC coin.
Of note is that the 500 & 1,000 btc bars dont have the firstbits printed at all.. they are lasered (if i recall).