Sorry this concerns and old comic, but I could not find anything on the internet about this.
Does anyone know why the symbol on supermans chest and cape are in the design of a ? mark near the end of issue 6 when he is taking off the face wraps and meeting with all the supermen from the future?
Ah, geez. Its been a while. Okay, in issue.....2.....or maybe 3 or so? Anyway, earlier in the story, mention is made of a device Superman is working on that allows him to communicate with his descendants through time. We get to see a short conversation between Lois Lane, and one of these future Supermen, "the unknown Superman of year blahblahblah".
In the scene you mention, Clark has, knowing he is dying, traveled back to the time of his father's death so that he can finally say goodbye. However, he cant run the risk of his past self (or anyone else) recognizing him, and he also remembers these events in this way, so he disguises himself as the bandaged Unknown Superman.
I dont recall if he was just disguises himself as such, or if it was implied that he actually, eventually, becomes the actual character. He is, after all, immortal in this story.