Likely a GT frame of some sort. Beyond that, no idea.
But there are issues. The rear wheel is smaller than spec, given the brake bosses are above the rim. Note how the front bosses seem appropriate for that rim. And that rear brake put onto it? Mounted on the wrong side of the frame, plus it looks like a walmart special brake. In fact, the bike strikes me as a bit of a frankenbike, where the frame has had parts moved over to it from a donor bike... and done so badly.
I would be concerned about the safety of that bike, just given the looks of it. Whoever put that rear brake on had ZERO clue. And I would expect that rear brake will break away at some point... while braking. Not good.
Better photos, with some close ups, might help. But you might also find more help at MTBR, assuming it to be an MTB or hybrid. The serial number can be useful as well, usually on the bottom of the bottom bracket shell. There are often clues there that you can use to find information online.
The rear of the top tube gives away GT so got that but Timberline did not have such a long head tube. If I'm wrong I'll eat it...I was 18 or so when I had one and 44 now. Interested big time in finding out.
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