This is the outline of an area with the preposition to placed inside the outline. Hence, it is an ideograph for the noun address.
Illustrative Text Reference:
Harappa: Seal: H-142 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 200: Collections in India: Suomalainen Tiedeakatemia.
Image Credit:
Indus Script Sign Number 385: Sign List of the Indus Script: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.