Wikipedia is wrong, as usual. The park announcer before Sherm was Fred Cusick who had the job for two years, 65-66.
Frank Fallon was a long-time sports guy at WUNR and WBOS and did Braves radio for a single season in the Jim Britt era. He was also the Bruins PA announcer at the Garden and was eventually succeeded by C's announcer Weldon Haire, who did both in the latter years of his career. Fallon did PA for the Celts in their first season before Haire took over.