Sharolyn,
Although I don't know if it is of any help. I have a Remington revolver that I have been able to research to a trooper in the 1st Missouri cavalry, Co.I & the bulk of the enlistees came from Indiana.
You might start a census check of counties surrounding Indianapolis for the year of 1860 & see if you can come up with a close match. Considering Miller is a common name, it might be a little difficult but can be done.
Also, a search of Missouri archives on the Internet can also be of help as it did help me.
Good luck.