The DEM-3000L model is a Development Kit prototype and the direct successor to the DEM-3000K. It was produced around Q2 2011 and delivered to Developers of bigger studios to work on their games before launch. It is estimated that approximately a couple hundred were produced. The motherboard is labeled with a "NEW DVT1" sticker which translates to Design Validation Stage Revision 1. 

While the form factor matches the final PDEL-100x dimensions already it design-wise doesn't resemble a final Vita just yet. The most noticeable difference is the glass faceplate which is missing both the "Vita" & "Sony" logo and still uses the smoothed edges design. Furthermore the main buttons are made of solid black plastic with the Dpad missing any prints and the analog sticks having a rougher surface. 

Although the back shell is final there is the typical "Not for sale" sticker which however now has a darker grey font-color compared to the previous K model.