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.
Comment:
The full height symbol for the noun ekka appears on tablets. It is possible that the tablets were used as tokens for vehicle hire.
Image Credit:
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.