What numbering system did the Romans use before the Etruscans ruled Rome?

Answer 1

We do not know whether the Etruscans ruled Rome and it is likely that they did not. The evidence base of the fashionable Etruscan rule/domination theory (invasionist theory) is flimsy. This theory has been questioned. More recent historians think that more recent archaeological finds in Latium (land of the Latins) suggest a different picture and there was no domination/invasion

Roman numerals as we know them are the result of their own evolution from their origin in an Italic tally system of notches carved into wood which was still used by shepherds in Italy and Dalmatia in the 19th century. This was not a system for mathematical calculations. It was ordinal, which means that it was used only to count and look at the relationship (order) between the tally marks. In fact, the Latin word for compute is ratio: (comparative) relationship. To think was ratiomen putare. Putare means to carve a notch. Rationem putare meant to establish a relationship (order) between the carved notches.

The tally marks were lines, instead of the letter I which was used later. They were added to each other, thus giving l (1), ll (2), lll (3), llll (4), etc. The 5th notch was turned into a double cut Λ (probably a hand with the 4 fingers together and the thumb apart). Initially the tallies could be difficult to read. E.g., 39 was given as llllVllllXllllVllllXllllVllllXllllVllll. Numerals then abbreviated the tallies, giving IΛ (4), ΛI (6) etc. E.g., 8 changed from llllΛlll to Λlll. There were various symbols for 50 which then became a ⊥ and later still was turned into a T. 100 was also given with several symbols and Ж came to predominate (X with a l in the middle) . □IC was also used and then became C because centum was the Latin for 100. 500 also had a number of symbols; Þ become common and turned into D because it was similar to the letter D. 1,000 was a circled of boxed X and then became the Greek letter phi Φ. This was the development up to the time of Augustus. Later, 500 became simply D. 50 changed from T to L. 1,000 changed further, Ψ and ↀ, then ∞, then ⋈. Finally, it became M because mille is the Latin for 1,000. With the linkage of tally symbols to letters, l became I, Λ (5) became V. The double stroke of Λ for 10 became X.