You mean Casascius bitcoin?
Are they ever really safe?
No record of the coin being compromised but I do not trust collectibles generally.
Even if they use the most secure possible way to hide/protect the private key doesn't the coin creator, who funded the address, have knowledge of that key?
The people that created the coin have knowledge of the private key.
There have been some collectibles that were compromised in the past because the creator knows the private key. This is the reason I can not get any coin with pregenerated private key.