Appears to be a race-type carb company based in Kentucky, from a quick Google. https://www.atminnovation.com/
I know of 2 different uses for "ATM". I wouldn't think much of someone using that acronym for car parts.
The carbs were built and delivered in a decent time. Came jetted pretty close to what was needed. Definitely ran out of the box and they were easy to work with. Once the car is done and I can put miles on it, I’ll be able to tell you more about the carbs. I have two of their E85 850s on my engine.