[1sembiyan]

It’s in a proto-sharada script, which it seems can be dated to earlier than 5th century.

There’s no consensus on dating of the Bakhshali manuscript however: https://www.ams.org/publicoutreach/feature-column/fc-2018-06

[arp242]

According to the article the proto-script emerged more during middle of the seventh century.

[1sembiyan]

Which article?