People are slowly realizing that small silver fractionals are the best option. With just the 5btc piece alone you could fill your safe with 1000's of silver coins funded with small amounts of bitcoin. Liquidity is easy. Make them $50-$300 value. Most everyone can afford it. Instead of trying to move 1 Million at a time. I look at them like money, not like collectables. No one carries 1 million in their pocket, but they might put a few $100 dollar bills in there and a few $20.
Its like having a 100 pound block of gold. Sure, everyone wants it, but no one wants it at the same time. You have to make it usable. You can turn that 100 lb block into 14,580 1/10th ounce gold pieces. 1/10 ounce gold pieces sell at a a much higher premium plus they are more affordable to everyone on the planet (About $250ea). Look at the Stack and Bower Auctions. The fractional pieces Win every single time. In percentage gains over the high denomination pieces.
The same goes with 30 btc. Everyone wants it, most everyone can't afford it or do anything with it except let it sit and sell/trade it as digital currency.
Lets just look at the 5btc piece. The BTC value is $276,000 +/-
At Stacks and Bowers they will get you that much, or it won't sell. Most pieces of this size bring 1.1-1.3 The higher ones are closer to 1.1. So maybe $300k if you're lucky right now.
ooooooor...
Turn that little nickel piece into...... 1000's of new fractional silver bitcoins.
I know what I would be doing, but that's just me.
You could send the 2 original Casascius pieces in to be professionally graded and framed for a nice keep sake to tell the story.
If that is something you want to do, PM me. I accept physical silver bitcoins as payment that we would create ourselves, because why not be your own bank.