Verified answer

Epi's can vary a lot, from guitar to guitar,

some were made in Japan, (the best ones)

Some in Korea,

Epiphone has also used China, (bottom of the pile)

India, Taiwan, and several other countries.

Not sure which countries, in which years

Too many to remember

The best ones, were the American ones, but they stopped that about 1970,

(except for a brief experiment, where they made a VERY few American Epis, around 1982-3)