I don't know - but the actual finish that's on the pistol is really well bonded, possibly rivalling even the quality of Umarex IMHO, certainly several orders of magnitude above that usually found on these type of cheap bb guns.
Usually aluminium can be anodised, steel can be blued/parkerised/plated and everything else gets paint.
I would say unless you were hell bent on polishing (and once you start you cant stop!) then the stock finish is best left - if i could have reversed my decision after trying to chemically strip it I would have