MtGox created some manual transactions with UTXOs that are unspendable. Even though these are in the spendable set, the conditions to spend them are impossible.

Abstract

First publically identified by genjix on https://bitcointalk.org/index.php?topic=50206.0 these UTXOs have a standard transaction script but with the flaw that they fail to push the public key onto the stack. Because there is no public key, no signature will satisfy these transactions. Therefore, all of these outputs are permanently lost.

Implementation

These UTXOs can be identified by checking to see if script_asm is 76a90088ac:

output.script_hex == '76a90088ac'

Example

Transaction 0ca7f7299dc8d87c26c82badf9a303049098af050698c694fbec35c4b08fc3df has this unspendable 100 BTC output:

      {
        "index": "0",
        "script_asm": "OP_DUP OP_HASH160 0 OP_EQUALVERIFY OP_CHECKSIG",
        "script_hex": "76a90088ac",
        "required_signatures": null,
        "type": "nonstandard",
        "addresses": [
          "nonstandard2cb6b5842f9d353ef44bb46407b03fed4673f4af"
        ],
        "value": "10000000000"
      },