This ideograph depicts two overlapping packs. It is the verb to exchange, to barter or to trade.
Illustrative Text Reference:
Mohenjo-daro: Seal: M-28 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 16: Collections in India: Suomalainen Tiedeakatemia.
Image Credit:
Indus Script Sign Number 403: Sign List of the Indus Script: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.