I could not find a listing for Roy Burch in any directory after 1934 (there was no directory for 1933). Ada Burch is listed in the Columbia directory for years 1936, 1938, 1939, 1940 at the same address of 601 Assembly Street. The Atlantic Coastal Life Insurance company is still an active company with headquarters in Charleston, SC. I don't see any "history of the company" listed, but you could call and perhaps they maintain a small library at their headquarters.
Good luck!