This article discusses software internally used by Apple.
Acquiring a copy without Apple's consent is illegal and may result in being scammed.
This build seems to be a later version of HoodooYabuli 9B3145a, and is also based off of an internal version of iOS 5.1. It was originally found on an iPhone 4S prototype. There seem to be little to no visual differences between HoodooYabuli 9B3176n and this firmware.