Apparently, an image of a Space Sheriff Gavan Ranger Key was leaked. This is in-line with the confirmation of the upcoming Kaizoku Sentai Gokaiger vs Gavan film this January.
Since it is also previously revealed that Bandai will release Space Sheriff Gavan's mobile headquarters, the Dolgiran, into a GokaiMachine — GokaiMachine Series EX DolGiran — the Ranger Key might came with this.
Even though the image contains ca3 blog's watermarks, it's highly possible that the image is fake and only featured a custom Gavan Ranger Key, since the image is not present in the blog itself.