Letter naming father of illegitimate child

[Peg Buckman]

Hi,
                                                                                                                                                                                                                                                                                                                                                                           On the birth record of my great grandmother, at GID 154.4.46200, # 50, August 1st, Charlotta Gustavfor, there is a note regarding a letter naming her father that can be accessed by proper authorities.  Can anyone tell me who I need to contact to find out what the letter says?  She is my great grandmother through her daughter Anna Maria who came to the US in 1901 and married my grandfather, Daniel Cushing.  I would like to trace the paternal lines.  Thanks for any help you can offer.