The script used in inscriptions in the northwest, known as Kharosthi, was deciphered how?

Comparison of coins belonging to Indo-Greek kings

The process of deciphering Kharosthi, the script used in inscriptions in the northwest, followed a different path compared to other scripts. The key to this decipherment lay in the finds of coins belonging to the Indo-Greek kings who ruled the region during the second-first centuries BCE. These coins featured the names of kings written in both Greek and Kharosthi scripts.

European scholars proficient in reading Greek were instrumental in this decipherment. They observed similarities in the letters used in both scripts when writing names, such as "Apollodotus." By comparing the two scripts, they found that the symbol for "a" appeared in both. With the identification of the language in Kharosthi inscriptions as Prakrit, the decipherment process extended to reading longer inscriptions as well. This breakthrough was attributed to the work of James Prinsep.