This isn't a post about the timeline of the Sentinels universe, but about the Sentinels publishing company.
So, how old is Sentinels Comics?
I got to wondering which characters represent "golden age" or "silver age" or whatever era of comic printing, and if some characters had been retconned / revised over the years.
For example, Haka seems like someone who got introduced early on with some problematic strereotypes (the big dumb maori), but then got refined into a more intelligent and complex character when a different writer got a hold of him.
When would the Freedom Four form? A lot of historic silver age teams tended to include only one woman, who largely acted as team mom, team girlfriend, and/or frequent damsel in distress. The Freedom Four Annual includes two women, both of whom have considerable agency, and one of whom is casually gay! This makes me think that the Freedom Four, and the introduction of Tachyon, is fairly modern. The annual also featured computer hacking, which would have been out of place anytime before the 80s.
Golden Age of Comic Books: if Sentinel comics was around, then I'm guessing their earliest WW2 era superheroes were (grandpa) Legacy and GI Bunker. After the war and the decline of superhero comics, they switched to westerns and horror comics. Some of those got recycled later on, with Silver Gulch getting re-used for time trival crossovers, some of the horror monsters showing up in the final wasteland. The Scholar may have started as a narrator for horror comics; a bindle toting drifter with stories of things he'd seen and heard on the road.
Silver Age of Comic Books: with the resurgence of superhero comics, Sentinel reintroduces a new Legacy and a new Bunker, creates the Wraith, along with some other classic heroes and villains. Any of their more four-color characters probably come from this era (frex: Chairman, Tempest, Ra, etc)
Bronze Age of Comic Books: this is when more minority characters started entering comics. I'm guessing that Black Fist / Mr. Fixer and Haka would show up around this time (and both get revised later into more complex characters). This might also be the likely entry point for any gay characters, like Tachyon and Medico.