Both late scholars Bhai Kahn SIngh Nabha and Bhai Vir Singh Ji have discussed the contents of this book in their writings. These writings were published well before 1955.
The original name of the book is Bhagat Rattanwali. The book is teeka and is based on the 11th var of Bhai Gurdas Ji. After the 12 pauri there are the names of numerous Gursikhs in which this book gives sakhis about these people. The book is based on both history and spirituality. Bhai Vir Singh Ji published the writings in 1912 and titled the book Sikha Di Bhagat Mala. Bhai Mani SIngh also had a teeka on the first var of Bhai Gurdas Jis writings and this book is called gyan Rattanwali. Both books are great and contain numerous qualities and rehats gursikhs should adopt to please SRi GUru JI .
Here is a short sakhi from Bhagat Rattanwali
One day a group of Gursikhs came to the sanctuary of Sri Guru Ram Das Ji and asked " How can we reach liberation?". Sri Guru Ji said one must do the following deeds: speak and practice truth ( naam) , renounce self-conceit, serve the SIkhs who come to your house, twice a day attend the place where kirtan is being performed, construct a Sikh place of worship in your village, wake in the early hours and bathe, medidtate on the holy name given at initiation, recite the morning hyms and conclude with the singing of Aarti. In addition, one should recite Sodar-rehras during the sunset, and continue by singing Gurbani kirtan. Finally one should conclude the day with the recitation of Kirtan Sohila.
ਸਤਿਗੁਰਬਚਨਕਮਾਵਣੇਸਚਾਏਹੁਵੀਚਾਰੁ॥