Below is the symbols listed by Theobald in his 1901 monograph. These symbols are noted mostly from punch-marked coinage in India datable to 10th century BCE
The symbol in the Obverse is called Indradhvaja or Indra's Flagstaff which is an image of a very large tree trunk or pole as explained by Rosalind Lefeber Valmiki in her book The Ramayana of Valmiki.
However I still couldn't find out the character on the reverse.
From my research, I found this character is similar to Kharosti script ( 3rd century BCE) below. It is resemblance to character JHA but with added stroke. Anyone has any idea?
Check below blogspot that display some of similar ancient clay seals and tablets from Indus Valley
Writing in Indus Valley
Item : Clay Seal
Dim : 10mm x 9cm
Weight : 0.6gm
Date : 2000 years old
Material : Clay