Your serial number indicates that your Springfield trapdoor model rifle was made in the year 1887.
on top, behind the loading gate, next to hammer
There are no model 1878s. You have a model 1873. Check out www.trapdoorcollector.com for more info.
made in 1887. caliber 45/70. vlue depends on overall condition. anywhere from $300 - $900 +
According to this proofhouse website http://proofhouse.com/colt/index.html the model 1878 was only made up to 1905 with the final serial number being 51210. I don't know how much your gun is worth but with a serial number 117187 it is not a model 1878
if it is the 1878 hammer shotgun made about 1886
With the hammer in the full down position look just to the left of where the hammer rests against the firing pin. You may need to open the action to read the entire number as it may obscure the last digit(s).
The Colt 1878 frontier model with serial # 35369 was produced around 1896.
Bigelow Cooper was born in 1878, in Springfield, Ohio, USA.