The hissa coins are an important part of the copper coinage of Akbar. We know that in ilahi 44, Akbar introduced a 40gms copper coin as Tanka. The hissa coins are fractions of that Tanka. Hissa literally mean 'part'. So the 20gms coin becomes 'Nim tanka' or half tanka. The lower denomination is written as 'Part' of Tanka. Hence half dam or 10gms piece becomes 'Chahram Hissa Tanka Akbarshahi' or '4th part of Akbar's Tanka', the quarter dam or 5gms piece becomes ' Hatam Hissa Tanka Akbarshahi' or 'Eighth Part of Akbar's Tanka' . Similarly the Damri or 2.5gms coins becomes 'Shanzdaham Hissa Tanka Akbarshahi' or '16th part of Akbar's Tanka'. There is a still a yet smaller fraction known called 'Si wa dom hissa Tanka Akbarshahi' or '32nd part of Akbar's Tanka'. For the Shanzdaham hissa in particular, there are Mintless and ones with mint specially Delhi mint. The Mintless ones are more difficult to get.
I post a set of Chahram, Hastam and Shanzdaham hissa for members