I have a variety of small (0.125 -0.5" marking area with either a curved or flat surface)parts that I need to be marked or quality control purposes.  I have looked at silk screening and pad printing.  I don't require any fancy serializing just a simple letter or number maybe one or two characters.  However, I need the printing to last 15 yrs and withstand temperatures of -40ºC to 125ºC.  As well, etching and other processes that remove material I would prefer not to use.  Processes that involved a baking process of more than 350ºF I would also not like to use since some of the features on these parts might warp.  I would prefer to have this marking done in house.  Can someone recommend a good supplier or source of information I can look up?  The material being marked can be stainless steel, brass or nickel plated aluminum.