Chris Reeve Small Sebenza 21 Night Sky with UFO is one of a kind, unique graphic into the handle by Lisa along with the inlay.

This Reeve Sebenza night sky knife has a UFO in between the trees

Letter "Z": This one has a single much taller mountain in a bit lighter blue anodizing compared to letter "Y".

Letter "U": SOLD

Source : https://www.plazacutlery.com/0-3140/Limited-Edition/Chris-Reeve-Small-Sebenza-21-Night-Sky-with-UFO.aspx

Plaza Cutlery is offering an exclusive Chris Reeve large sebenza 21 with Dog Paw gold color anodizing w/o bead for sale at $485 only. The front scale is ground smooth then the "gold" tracks are added! Also the blade has the fine belt finish for a little nicer look! 

Source : https://www.plazacutlery.com/0-1735/Frame-Lock-Large/Chris-Reeve-Large-Sebenza-21-with-Dog-Paw-with-Gold-Color-Anodizing-w-o-Bead.aspx