The Romans were slow to adopt the use of modern coins for financial transactions compared to their more sophisticated neighbors, the Greeks. In the fourth century B.C., the Greeks were using coins made of precious metals, while the Romans were still using bronze. A sample Roman trade equivalence was:
1 ox = 10 sheep = 100 lbs bronze
More often than not, goods were traded without using money. The use of heavy lumps of bronze, which had to be weighed at the time of sale, was extremely cumbersome.
When the Romans finally started making lighter coins in the fourth century B.C., they featured images of animals as a representation of value. The Roman word for money, Pecunia, comes from the word pecus or cattle. These coins, called Rudes, were one pound lumps of bronze.
The dominant coin of both the Republic and the Empire was the silver Denarius, which weighed 4 oz. When the Denarius was first struck in 211 B.C., its value was,
1 ox = 10 sheep = 60 Denarius.
Roman soldiers were paid 120 Denarii per year until 50 B.C., when their pay was doubled by Julius Caesar. Some additional examples:
A cavalry horse cost 312 Denarii
A slave cost 300 Denarii
A tunic, toga, and sandals could be purchased for less than 100 Denarii.
The Denarius lasted 450 years as the most common Roman coin (211 B.C. – 243 AD).