This image of signature is taken from a letter of Subhas Chandra Bose, who is presumed to have died in absentia in 1945, see article Subhas Chandra Bose for more details about his death]]). The letter was written in 1933. So, it is already almost 80 years. And this is a too minor work (only a part of a letter). Moreover in India, Subhas Chandra Bose is considered as a national hero, and all of his known photos etc are used freely without any restriction.
Licensing
Public domainPublic domainfalsefalse
This signature is believed to be ineligible for copyright and therefore in the public domain because it falls below the required level of originality for copyright protection both in the United States and in the source country (if different). In this case, the source country (e.g. the country of nationality of the signatory) is believed to be India.
Note that this tag cannot be used on all signatures, as not all signatures are copyright-free.
This work is in the public domain in its country of origin and other countries and areas where the copyright term is the author's life plus 70 years or fewer.
You must also include a United States public domain tag to indicate why this work is in the public domain in the United States.
Note that a few countries have copyright terms longer than 70 years: Mexico has 100 years, Jamaica has 95 years, Colombia has 80 years, and Guatemala and Samoa have 75 years. This image may not be in the public domain in these countries, which moreover do not implement the rule of the shorter term. Honduras has a general copyright term of 75 years, but it does implement the rule of the shorter term. Copyright may extend on works created by French who died for France in World War II (more information), Russians who served in the Eastern Front of World War II (known as the Great Patriotic War in Russia) and posthumously rehabilitated victims of Soviet repressions (more information).
Got a better image (sig) where both English and Bengali signatures are displayed. Need to change image source, will do it right after uploading the image.