The Indus Dictionary Project
This Indus sign resembles a leaf from archaic variants of the Chinese word mén 門, which Xu Shen said was comprised of two hù 戶. It is a door or gate leaf.
In the context of the sample text, the symbol is an ideograph for the verb to open.
Lothal: Seal: L-86 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 258: Collections in India: Suomalainen Tiedeakatemia.
There is only one extant example of this Indus sign.
It is interesting to note that Champollion states that a pictograph of a door leaf was used as an ideograph for the verb to open¹. Although, the Egyptian symbol for a door leaf differs from the Indus symbol, this is an example of common usage for the equivalent character in the two scripts.
Door Leaf: Lynn Fawcett, 2017.
1. Jean-François Champollion le Jeune, 1841: Dictionnaire égyptien en écriture hiéroglyphique: Chapter 5: Edifices en Construction: Paragraph 260: Manuscript Page 251: Firmin Didot, Paris.