The major player in my next Traveller Campaign is the 'Polity.' I think FFE has copyrighted 'Imperium.' The Polity is made up of humans descended from Terrans who were abducted/saved at the end of the last Ice Age by aliens we'll call the Ascended. The Ascended ... ascended eventually. They evolved to the point where they no longer really had any cultural references with us lowly meatbags anymore. The humans left behind had access to their technology and managed to back engineer some of it with different degrees of success.
Like the Terrans who arrive on the Up Port the Polity is about TL 9. They have gravitic drives and laser rifles and carbines. Their troops wear ablative (think chrome storm troopers who can hit what they aim for sometimes.) The Newcomers will probably assume they are much more advanced. The problem is a) the Polity is a stagnant culture (these humans are not as technologically inclined as the humans left behind on Terra) and b) having grav drives made much of the technological innovations of the Terran space age unnecessary. The constraints of primitive chemical rocket launch systems led to miniaturized electronics, robotics and other goodies the Polity never needed.
The Polity has also struggled to maintain their grav-tech and FTL drives to keep an edge over the other cultures in their cluster. Other areas of technology are pretty much ignored. So IT is about TL 8. They have fusion reactors (made possible with grav tech to contain reactions) though they seem to guzzle fuel because the ignition procedure is very energy intensive. Their sensors are quite primitive by modern standards because in general their ships jump pretty close to the world they're heading for.
The grav drives they use have several interesting features. Each gee of the drive rating can be used to accelerate at 10m/s^2, compensate for 1 gee of acceleration, or create a barrier against incoming weapon fire (their armor materials are also only TL 8.) They have typical 70's space opera tech.
The Newcomers however have advanced armor materials, point defense, sandcasters and smart weapons. Will their more realistic technology be a match for the retro future technology they face?