Listo.. encontré la respuesta!
YYMMFFRRRRR -- new model codes, no letter prefix
Beginning 2008-09 models are appearing w/o a letter prefix to i.d. the factory. Based on what is reported so far, it appears that the serial code may be:
YY = first two digits = year of manufacture
MM = second two digits = month of manufature
FF = third two digits = factory i.d. where made
RRRRR = remaining digits = ranking number
Fábricas
11 = MIC sticker on a '08 Masterbuilt 500
12 = DeaWon or Unsung (China -- uncertainty remains as to which factory)
15 = Qingdao (China) -- electric
16 = Qingdao (China) -- acoustic
17 = (China - factory still unknown) MIC sticker on a J160E
20 = DaeWon or Unsung (China -- uncertainty remains as to which factory)
21 = Unsung, Korea
example 08121520333 was made in December 2008, factory 15 (Qingdao-China - electric div), 20333 unit produced