Found a few early 3DS SDKs. The only 2010 one is armcc_4_1_nintendo-b561_20101020. The 2011 set is more complete. The main one being Nintendo 3DS - NintendoWare for CTR (World) (2_0_3-SDK2_3_4-20110518). This is strange, because NW4C_CreativeStudio.exe exports to the final bcres/CGFX format.
Exe last modified: May 18, 2011, 1:59:34 PM
Animal Crossing New Leaf final has three older format models:
Strc\Shadows\bench2x1_shadow.bcres
Strc\Shadows\lamp_shadow.bcres
Strc\Shadows\my_home_shadow.bcres
I originally thought they were 2011 models, but now it seams late 2010, or January/February 2011.