As far as I know, GEM razors were made in the USA, while Ever Ready razors were made in England. It is likely that the Ever Ready razors that look like GEMs were made under licence.
Normally the 'G' on G bar razors for example would be on a circular panel on the handle, but Ever Ready 'GEM' like razors would have a blank circular panel. But it sounds like you either have a hybrid razor - a head of one fitted to the handle of another by a previous user, or that there was a crossover period where razors early in the production run had this dual branding.