Bonjour Ralph2093!
The Aeromarine 39-B was built by the Aeromarine Plane and Motor Company in Keyport, New Jersey. The aircraft are described as, in United States Navy Aircraft since 1911 by Swanborough and Bowers, as "conventional two-bay wood and fabric biplanes and could be fitted with wheels or floats". The Aeormarine 39-B was powered by the 100 hp Curtiss OXX-6.

A photograph of the Aeromarine 39-B making the initial landing on USS Langley piloted by Geoffrey DeChevalier on October 26, 1922.
The book referred to makes no reference to an Aeromarine 39BL ... The Aeromarine 39 is described and illustrated in The Encyclopedia Of World Aircraft edited by Eden and Moeng, but, no notation of a BL version is made. Where did you learn of the mysterious variant?
Bonne année
Kirk