Based on the stepped keys, I'd say it's probably XT, too. All you'd have to do is the steps at
viewtopic.php?t=19035 and get the correct pinout. (FWIW, I'm working on another thread where I'm having difficulties with pinouts, so I can't help more.) I've seen snacks posting here, before. That's not exactly a username you'd forget

.
The color of the Space Invader slider doesn't really apply to anything, so you could have a clicky, tactile, or linear keyboard.
Considering the top case is only slightly yellowed, you might want to clean it and leave it out in direct sunlight for a week, rotating it 90 degrees every day (don't do this if you have temperature extremes or if you're expecting bad weather).
I like using Simple Green sprayed onto a lint-free cloth for cleaning the top and bottom case. You can use one of those Mr. Clean Magic Eraser things for really stubborn spots, but a) don't soak the pad (water + electronics don't mix) and b) note that the Mr. Clean Eraser is really a fine-grain spongy bit of sandpaper, so don't go overly nuts in one spot.
The keycaps look very nice and you can just clan them off by CAREFULLY removing them and soak them in warm, slightly soapy, water, for a bit. Then use a cloth to clean 'em off. An ultrasonic cleaner works great.
The Wiki article on Hi-Tek 725 keyswitches is at
wiki/Hi-Tek_Series_725.
I've got a Space Invaders keyboard that still needs some attention, but it really is an interesting 'board.