Tiagra 12 II Main gears Material?

[gstours]

Quick question.  Are the main gears used in the tiagra 12 size reel brass or stainless steel?  I have a tiagra 16 and 20 and 30 and they are stainless.  I was wondering if the 12 reels are issued with the brass main gears as I have heard???   Does any body know?  I think they are interchangable (16-12) main gears.   Correct me if I am wrong,  but isnt a 12 just a narrowed frame 16 reel?
   Thanks for some feedback,  and experience with this question.      gst.