BLOG: Custom Metal Gear REX by Armament Factory – W.I.P. Part 1
Scale: Non-Scale (larger than MGR-1 pattern, smaller than MG-RX1 pattern)
Material: Scratchbuilt with PVC & Styrene
So yeah, the one at the top is the commissioned piece in construction while the one at the bottom is the 1/100 scale Metal Gear REX as seen here.
Image © ~ARMAMENTFACTORY