Codename/Project Denver

Microsoft Denver, also known as Windows Denver, Codename Denver or Project Denver was a cancelled Windows Server release with only 2 known builds, Build 4552, complied on March 18, 2012 and leaked July 23, 2014 (well after the Denver project collapsed) and Build 4566, which was never leaked but could have been complied sometime from March 22 to March 26. It is noted that the leader of the Denver project resigned after 4566 and the project therefore collapsed.

History
Companies with much smaller and older servers were complaining that they were occasionally stuck on Server 2008 as 2012 R1 refused to install, Microsoft, wanting to fix this, got a small dev team together and formed the Denver team in late January 2012, according to some theories the first build was 4526, complied in early February, but no evidence supports this claim. By early March they are believed to have had a working build, leading to 4552 being complied on March 18. Afterwards Build 4566 entered development and was complied thereafter, however...Fred Scott, the face of the Denver project resigned after 4566, and Microsoft could not find a replacement. They officially killed the Denver project on April 2, 2012. Instead the employees were put into Windows Server 2012 R2, released the next year, and it acted more friendly to the older servers. A few photos of Project Denver were released on July 23, 2014 on a BetaArchive forum post before the .iso was uploaded just 45 minutes later. The screenshots are shown below. (Note, the update will be very shortly.)