Vintage Simmons Drums (UK) Users Group

Hi All,
      I found a eprom that is a 27128A. I know that the 2764 is used 
for the bass and snare drums and the 27128 is for toms. 
      What does the (A) mean on the Eprom that I found and can it be 
used in the SDS EPB unit to be used in my SDS7 brain.
      If someone can help me out with this that would be sweet.
                                              Haley