The Sarbloh Granth, the volume of all-iron, is a further text attributed by the Nihang and Damdami traditions to Guru Gobind Singh Ji and not accepted as his by mainstream Sikh scholarship or by the SGPC.
It is a long narrative work in Braj on a war between gods and demons, with a substantial section on the qualities of the Khalsa which is where the well-known formulation about the Khalsa as the Guru's own form appears.
It is installed and read in some Nihang deras alongside the Guru Granth Sahib Ji, which the mainstream position does not permit.
Its manuscript history is thin and its authorship has not been established.
It is included here because a project about Punjab that only reports the settled mainstream position is not reporting Punjab. The Nihang dals are three hundred years old and this is their text.
The Nihang deras treat it as a Guru's composition and read it as scripture. The mainstream Sikh institutions do not, and there has been no formal adjudication of the question.
Its language and its subject place it in the same literary world as the Braj works of the Anandpur and Paonta period, which is the strongest argument its supporters make.
There is no critical edition. The printed versions in circulation derive from a small number of manuscripts held in dera custody and have never been collated.