The first step in researching your about 1939 Long Range is a documenting letter
The ventilated rib could have been an after-market add on, and the gun may have been used for Trap. If original, it would certainly be rare. Dr. Jim's "L.C. Smith Production Records" lists < 1% of LRWF with Vent Ribs.
Lot of information here
Also look through the FAQs and be aware that any non-expert cleaning/refurbishing may substantially lower the value of the gun, which might be significant depending on the provenance.