That looks like some sort of trimmed off hemispherical lens. I was looking for aspherics a while ago and found it, it can save me quite a bit of hook up work over a 80 × 60mm heatsink for an old gooseneck lamp whose emitter configuration will be 2x in parallel 6V ∅20mm quad boards with an LH351D in series with two LH351Bs in parallel each (6 emitters total). Just some good glue and done. 
The question of course is what sort of beam will it render. To me it looks to work sort of like a wide angle aspheric, albeit the emitters will lay inside.
Cheers ^:)
