BTC wallet recovery: I have a 12 word backup, what do I do? I have the 12 key seed phrase from a 10 year old Bitcoin-qt acct, but don't know what tool to use to turn it into a wallet. Obviously I am terrified to put the seed phrase into any ONLINE tool. I want to practice offline somehow to see if I even wrote it down properly. I tried looking thru the sourcecode: https://github.com/bitcoin/bitcoin to see there is a word-list.. No joy.  One guy said Electrum, but it didn't help decipher the individual words, just kind of a 'put them all in', sink or swim endeavor....
Try this,
https://wallet.mycelium.com/
YOu may find more relevant information here as a second option.
https://wiki.trezor.io/Welcome