First Marvel / DC crossover and second co-publication, after MGM's Marvelous Wizard of Oz. Next crossover is Marvel Treasury Edition #28 featuring Superman and Spider-Man.
According to Overstreet, there are 5,000 numbered issues signed by Carmine Infantino and Stan Lee. Based on information gleaned from several internet postings and sales, it appears that only 2000 copies were in the signed edition. Furthermore, because Carmine Infantino was no longer editor at DC as of the end of January 1976, it appears that only a fraction of the 2000 copies were signed by him (at least from #431 up do not bear Infantino's signature). All copies were signed by Stan Lee. Overstreet's claim of the signed copies being a second printing is not supported by any data on the comics themselves.