Lemon Meringue Pie build LRW87D has been spotted in the Chromium issue tracker, the build is running on a Hammerhead device, better known as the Nexus 5. The build was found in a bug report about an issue about crashing videos and also includes a small movie showing Android L build LRW87D live in action.
Starting with Cupcake, individual builds are identified with a short build code like LRW87D . The first letter is the code name of the release family, e.g. L is likely Lemon Meringue Pie. The second letter is a branch code that allows Google to identify the exact code branch that the build was made from.The next letter and two digits (W87) are a date code.
The letter counts quarters, with A being Q1 2009. Therefore, W is Q3 2014. The two digits count days within the quarter, so W50 is September 25th 2014. Finally, the last letter identifies individual versions related to the same date code, sequentially starting with A. So D is the fourth version of that day.
Google states on their website that the date code is not guaranteed to be the exact date at which a build was made, and it is common that minor variations added to an existing build re-use the same date code as that existing build.