Nostalgia is a brand of perfume or cologne created by Veidt Enterprises. Advertisements for the perfume appear throughout the events of Watchmen. The poster has the tag line "Oh, how the ghost of you clings" and an image of a woman adjusting her stockings. According to a letter from Adrian Veidt to Angela Neuberg, director of Veidt Cosmetics & Toiletries, they choose slightly androgynous women to appeal to the gay market.
According to Veidt the success of the range is down to the romantic atmosphere and soft focus of the ad campaign. The marketing strategy conveyed an idyllic idea of a modified, half-remembered past due to a withdrawn sense of global uncertainty and the belief of an unstable future among the populous.
The Nostalgia line would be discontinued after the attack of the Alien Monster to make way for a new line called Millennium, which will feature more controversial imagery to reflect a utopian vision. The new line would be ready in the summer of 1986. Posters for this new brand can be seen on the last pages of Chapter XII.
Nostalgia is representative of the characters' reminiscences, memories and flashbacks. This is particularly notable in Chapter IX. In the end of Chapter XII, the shift of focus to the new Millennium brand represents a larger change in the characters, looking less towards the past and more towards the future.
It's made obvious that Veidt used the brand and marketing of Nostalgia as a manner to make people long about an idyllic past and be uncertain about a shadowy future. More certainly, the contrast between Nostalgia and the later Millennium, would make the buying market conform more effectively to his new utopia after the threat of the nuclear war.
Similiarly, it's made obvious that Mmeltdowns/Sunbursts are a product of Veidt Enterprises, who used this change deliberately in order to manipulate this change of interests of the buying market (the way he altered Nostalgia to Millennium).
Also when the investigation in the Comedians apartment is happening, a bottle of Nostolgia is seen on a dresser. Which hints that Adrian Veidt is behind the Comedians murder.
DC Universe Rebirth
Following Watchmen's integration into the DC Universe, a character known as Mr. Oz (heavily implied to be Ozymandias) is shown to be covertly monitoring the current Superman. An agent operating on behalf of Mr. Oz bears a tattoo on her forearm, a circle with a Z running through it, heavily resembling the Nostalgia logo.