I picked up this brass lens a while back and finally got around to playing with it. It's around 4" long and alomst 2" in diameter. Seems to be around 130mm in focal length and was hacked up to add an aperature that's marked as f6.3 and seems to be close. Doesn't cover 5x7 and I think it will barely cover 4x5. I assumed that the threaded end is the end that's meant to attach to the lensboard and face the back of the camera. But, when I mounted the lens "backwards", it yielded the result shown (that's a portion of the top of the frame, taken off the groundglass with a digicam). Is that the petzval swirliness I've heard so much about? I'm going to load up a grafmatic and give it a try tomorrow but I was wondering what the petzval experts could tell me.