This is a very interesting type of manuscript. The origin of this manuscript is Dhaka, Bangladesh. The script is called abugida, and written in Bengali language on thin papers both sided sandwiched by 2 hard boards.
I dont have much information of this kind of manuscript & its writing tradition. Below are excerpts from Wiki :
The Bengali alphabet (Bengali: বাংলা লিপি bangla lipi or Bengali: বাংলা হরফ bangla horof) is the writing system for the Bengali language. The script with variations is shared by Assamese and is basis for Meitei, Bishnupriya Manipuri, Kokborok, Garo and Mundari alphabets. All these languages are spoken in the eastern region of South Asia. Historically, the script has also been used to write the Sanskrit language in the same region. From a classificatory point of view, the Bengali script is an abugida, i.e. its vowel graphemes are mainly realized not as independent letters, but as diacritics attached to its consonant letters. It is written from left to right and lacks distinct letter cases. It is recognizable by a distinctive horizontal line running along the tops of the letters that links them together, a property it shares with two other popular Indian scripts: Devanagari (used for Hindi, Marathi and Nepali) and Gurumukhi (used for Punjabi). The Bengali script is, however, less blocky and presents a more sinuous shape.
The Bengali script evolved from the Siddham, which belongs to the Brahmic family of scripts, along with the Devanagari and other written systems of the Indian subcontinent. In addition to differences in how the letters are pronounced in the different languages, there are some typographical differences between the version of the script used for Assamese and Bishnupriya Manipuri as well as Maithili languages, and that used for Bengali and other languages.
Item : Antique Bengali Hindu Manuscript
Content : Hindu Ritual
Dim : 10" x 3" x 0.5"
Date : 18-19th century
Copyist : anonymous
Origin : Bangladesh
Calligraphy : Abugida
Design : Written in Abugida scripts in black in Bengali language
Purchased Price :US