I starting questioning this locomotive here, back in 2011, and have been off-line for a few years now. I'm glad that this NG forum is still here.
I believe that the locomotive is the "1876", later to see service on the Manhattan Beach, as the C.L.Flint. It is the only one on their roster to have the smaller 36" drivers, as opposed to 42" for the others. There is more space between the top of the wheel & the running board in the Grafton Centre RR photo with the combine. Also, for another oddity, the combine, I believe is the original Martha's Vineyard RR "Dummy", and was nearly identical to the other "Dummy", which was the original motive power on the GC RR. I have other notes & research that I've gathered over the years, but alas, most are in storage in my garage, which is a bit cold this time of year in New England. Thank you for letting me chime in on this topic.