Texet is a UK company (Manchester) that has been involved in consumer products, including calculators and other stationery, since 1959.
They’ve released two game calculators that I’m aware of with their branding; the GM-116 Grabman and this one, the AD-115 Astro Destroyer. There are certain similarities with others – the Jumble JM-125 and the Bull Fight BF-114 which all may have been made by Taiwanese company Zykkor and rebadged by a number of different distributors (I’ve seen the Astro Destroyer with a Technico brand and also an unbranded version).
Regardless of its pedigree, the space invaders clone has two unique games. The first involves you shooting at two marauding invaders as they seek to land. There’s also a mystery ship that appears periodically. Game 2 is more like the arcade Space Beam where the mystery ship appears along the top in one of three locations and you have to return fire before their beam hits the earth; to win you have to anticipate where it is going to appear and shoot first.
The games are fun enough, probably only because they are teamed with a calculator so gave a welcome diversion from maths class or homework. The sound is quite basic, but at least it has sound.
There’s also a clock, unless you turn the calculator off at which point it resets to 12:00:00 — odd, since it’s really easy to move the switch one extra click from Time to Off without realising it.