As for as we know, only three publishers created boxed sets of their Gor books: Ballantine, DAW, and Star. All of these publishers might have published other boxed sets, that we still don't know of. Here's what we do know off.
Ballantine published a four-volume boxed set, entitled Tarl Cabot of Gor, with ISBN 0-345-24793-0, during the second half of 1975. A year later, during the second half of 1976. they released a five-volume boxed set, also entitled Tarl Cabot of Gor, with ISBN 0-345-25598-4.
Presumably around 1980, possibly in March, DAW published a three-volume boxed set, entitled Gor 1 - Deluxe Gift Set, without an order number, and a four-volume boxed set, Gor 2 - Deluxe Gift Set, also without an order number. Also in 1980, presumably later that year, DAW published a First Printing and a Second Printing of a five-volume boxed set, simply entitled Deluxe Gift Set. In 1981, they released two other four-volume boxed sets, entitled Gor I - Deluxe Gift Set, with order number #PR1122 and Gor II - Deluxe Gift Set, with order number #PR1123. Note the use of roman numerals for these last two sets.
Star published at least three three-volume boxed sets, all entitled John Norman's Gor: Boxed Set (Tarnsman, Outlaw and Priest-Kings) and Boxed Set (Nomads, Assassin and Raiders) in 1984, and Boxed Set (Blood Brothers, Kajira and Players) in 1986.
Here is a cover gallery showing all the editions and printings of Boxed Sets, sorted by year of publication. Click on any cover to see the book.
Here is a cover gallery showing all the editions and printings of Boxed Sets, sorted by edition. Click on any cover to see the book.