I guess before I bid on any Flathead blocks on eBay, I would certainly want to see a magnaflux certificate. Without it, would seem likely that a guy could end up with quite a collection of cracked flattie blocks!!!!!! If someone is warrantying a block (or any part for that matter), it would seem he should be able to offer some sort of proof that his flattie block isn't cracked!!!!! JMO