Mainly because if there wasn't peace, the colt 45 was quick to bring it. Either by threatening those not being peaceful or removing the problem.
Colt .45 The colt model p had the nickname the peacemaker.
The age and value of a colt .45 peacemaker serial 180356 are about 1900
Proofhouse.com
Call Colt and they will tell you.
http://www.wyattearp.net/buntline.html
1915
A .45 caliber Colt revolver- a handgun.
You want to ask "What was considered 'The Peacemaker'", which was the 1873 Colt Single Action Army revolver, generally in .45 Colt caliber although it was produced in many different chamberings.
When it came out it was *$17.00*
value depends on overall condition..........
50-1000 USD or so
No way to tell caliber by sn. You will have to call Colt.