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
Impossible to answer without the serial number.
Random Number Generation algo
what is the age of a .36 cal pedersoli black powder rifle serial number da89669
the serial number is needed for the manufactured date
Mine is on left side by site on barrow
There is a strong likelihood that it does not have one. Serial numbers were not required by law on rifles and shotguns until 1968. If the shotgun is a muzzle loader that uses loose powder and shot, it is considered an antique firearm under Federal law, and is not required to have a serial number.
about 1913/1914
50-100 USD
You must take it to a gunsmith to find out.
100 or so
10-100 usd
20-300 usd