As Grimble is my surname, I am very interested wherever it occurs, and have created 17 family trees of Grimbles, both those that trace back to English origins, as well as Afro American Grimbles. I believe I can help you with your query, as I think JB Grimble was known as Junior B Grimble, born 1910 in Franklin, La, and appears in the 3 following censuses,lastly in 1940, as a single man, a farm labourer in Richland, La.
Let me know if you wish to follow this up. I can be contacted also by email firstname.lastname@example.org
and I live in SE London.