Matt Walker informed me that the 2009 BTOW gain calibration he performed was on RCF in the directory ~staremc/2009/pp200/.  While we cannot check the trees themselves against those made in 2010, which were deleted before being backed up to HPSS, I have tried to do checks against the root files and codes that are left in Matt's directory. 

Matt's directory contains 2009.all.mip.root, which is the result of bemcCalibMacro.C (which makes the trees) and mip_histogram_maker.C (which makes the histograms).  Even though the changes I  made to mip_histogram_fitter.C were almost entirely cosmetic, I ran my version of mip_histogram_fitter.C over Matt's 2009.all.mip.root.  The results show excellent agreement:

(Matt's gain - my gain)/(Matt's gain)

Therefore I can conclude that mip_histogram_fitter.C is the same as the one used in the original 2009 calibration.  Furthermore, my version of mip_histogram_maker.C is identical to the one in Matt's directory.  Therefore any differences that we see between the MIP calibrations are due to the trees themselves (which we know have different statistics and come from different run lists) and are not due to the mip_histogram_*.C codes.