|The following is based on the canceled Fallout movie and has not been confirmed by canon sources.|
The old promo tape is mentioned as part of the supply inventory of Vault 13. On it is a promotional video on the use of the G.E.C.K., "which explains the G.E.C.K. is a miraculous, one-shot terra forming device to be used by the Vault Dwellers upon eventual emergence onto the surface."
It is more than likely that, as part of the Fallout universe, the tape was a film to be projected onto something, much like the projector used in Fallout 3 when the Lone Wanderer takes the G.O.A.T. Unfortunately, there is no evidence for this, and the actual characteristics of the tape are unknown, as is the method of viewing it; this is due to the film never progressing past its inception stage.
The only time a G.E.C.K. promo tape makes an appearance in the film is in Vault 13, where Hero watches it as part of his daily routine. However, due to the identical nature of the vaults, it is likely all the southern Californian vaults had one.