This coin was part of a lot of coins I bought awhile back ago. I don't know much about Roman Republic coins so Bob here at the forum helped me out a bit.
Quote: ,,, is a bit of a challenge since there were several moneyers who issued Roma denarii with an X under the obverse chin, with no obverse legend to the right, and with a quadriga reverse.
There appears to be an "M" starting the word to the right of the horse's legs, which leads me to believe that the issuer may have been M. Papirius Carbo (M CARBO)...but this may be another coin you'll have to get under a loop to tell for sure.
Well I got it under a loop and yes there is a "M" there - good eye Bob. But I also see that I have a fouree - that's a pretty cool suprise