This is a pictograph of five counting rods. It is the numeral five.
Illustrative Text Reference:
Mohenjo-daro: Seal: M-331 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 84: Collections in India: Suomalainen Tiedeakatemia.
Comments:
It is interesting to note how the arrangement of the counting rods is the same as the second and third rows of a stack of ten counting rods. In other words, the symbol reflects the actual usage of counting rods.
For the avoidance of confusion, please note that the three full character height lines followed by two slightly shorter lines, in inscription M-1202 c, reads summer road. It is not a variant of the numeral five.
Image Credits:
Numeral Five: Lynn Fawcett, 2017.
Ten Counting Rods: Lynn Fawcett, 2018.