The 7 coins thing was solved pretty quick, and the special emblem was awarded only to the first person to find them all and tweet pictures of them to Bungie. It was pretty much completed day 1. There has been a prevailing rumor that is at least 1 more chest is the Vault of Glass. There are 5 known chests: The one after you open the door, the spirit bloom chest, the Templar no teleport special chest, the Gorgon maze exotic chest, and the right path chest in the Gorgon maze. The vast size of the Vault, some secret areas that feel like they should be used somehow (such as the Vex gate at the end of the jumping puzzle). and Bungie's obsession with the number 7 have led to the belief by some that there are 7 chests in the Vault. Despite many theories, tests, and even claims of success, there has never been any proof that these additional chests exist. An additional part of the rumor claims that during an interview, someone from Bungie said that there were still secrets in the Vault. Again, no one has been able to submit proof that Bungie said this. The most controversial rumor is that everything included in The Dark Below and House of Wolves expansions were originally slated for vanilla release, but were held back at the behest of Activision to be sold as DLC. While there is some circumstantial evidence to support this, the truth is no one really knows. Bungie has stated in numerous interviews and releases that all the major components (that being everything except the art and environment assets) in TDB and HoW were built after the vanilla game was completed and turned in or "gone gold". Without irrefutable proof either way, there will likely always be questions regarding this issue. There are many more interesting rumors regarding the lore within the Destiny universe.