Brooklyn Machine Works

^^this is just educated guesswork, but looking at that frame it's top tube doesn't meet the seat tube high enough to be a long, or low enough to be a short. it's easiest to tell when they're built up, if the top tube points to the tyre/top of rim then it's a medium, above then its a long, halfway between rear axle and rim then it's a short

I've measured the top tube and the seat tube and they're the same as the specs for the long. I'll post a picture once it is built up.