Where can I obtain an owner's manual for a Beretta BL-series shotgun?

Owner's Manual

The over and under models BL correspond to the Beretta Italian model
known as 55. Manufactured by Beretta Italy and exported to US under that
name. A dedicated manual for these models was not produced. Because the S55, from the point of view of field stripping and safety procedure, is the same as the 680 series, the 680 series manual can be used. The 680-series manual and some old instruction booklets are attached for reference.