I have the same package as you on my truck and what I determined is that ATR sold three different turbo packages including the Downpipe, wastegate, and the turbo. The turbo seems to be a Garrett T3T4 setup. The only difference I can see between yours and mine is that on your housing it says "A/R 50 M24" of where mine says "A/R 60 M24"
I thinK this is the ATR Catalog that has the turbo, Downpipe, and wastegate
http://www.syty.net/forums/showthread.php?t=79954&highlight=atr+catalog
I only have pictures of my turbo, and I dont believe I have any from when it was installed on the truck, but mine looked identical to yours except I had the 90 degree inlet elbow going into an ATR cold air box, and mine was Air to Water intercooled