Mahadevan's sign number 4497 appears to be a full height variant of the noun ekka or light carriage.
Sample Text Reference:
Harappa: Tablet in bas-relief: H-1943 B: Asko Parpola, B. M. Pande, and Petteri Koskikallio, 2010: Corpus of Indus Seals and Inscriptions: Volume 3,1: Page 266: New material, untraced objects,
and collections outside India and Pakistan: Suomalainen Tiedeakatemia.
The full height symbol for the noun ekka appears on tablets. It is possible that the tablets were used as tokens for vehicle hire.
Indus Script Sign Number 4497: List of Sign Variants: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.