The underlying language has not been identified though some 300 loanwords in the Rigveda are a good starting point for comparison.[36][37] The average length of the inscriptions is less than five signs, the longest being only 26 signs long[38], although recent findings have revealed copper plates belonging to the mature Harappan period, one of them having 34 characters inscribed onto it.[39] No bilingual texts (like a Rosetta Stone) have been found.