I bought this from Insurrection Vintage in 2011. Now they sell through their "Thurston Brothers" website.
They used to have a deal with Aero where their Cafe Racers would get an extra inch in the length of the arms and the body. I wanted both of these since I was buying this to wear while actually riding a motorcycle.
I ordered a size 42 and it fits perfectly. I'm 5'10" and 180 with an athletic build. My actual chest measurement is 39". This is a very trim fitting jacket, I can layer under this jacket if I don't need to bend my arms, lol. Actually, bending my arms is difficult even in a t-shirt, because the leather is so thick and stiff. For example, I can't talk on the phone wearing this jacket because the leather is so thick at the bend of my elbow I strain to hold the phone to my head.
Because of that, I rarely wear it as a casual jacket. This is nearly 10 lbs of leather, you never forget you are wearing it. Also the cut of the jacket is such that when it is unzipped it pushes the back of the collar up against the back of your neck. It's also cold in the winter, I struggle to find thin, thermal tops to wear under it.
But those are quibbles really. I wanted a motorcycle jacket and it's perfect for this. I love the way this jacket is breaking in and wearing in. It's Horween CX horsehide, which is surface dyed. So as it wears, the brown underneath begins to show through and it gets better with age. The thick, heavy leather will earn it's keep if I ever find myself sliding down the road on my back.
I did have the zipper modified on a trip to Insurrection in Seattle. (Awesome customer service, can't say enough good about them.) Originally the zipper went all the way to the hem. I had it replaced with a zipper that starts about three inches above the hem. This allows the hem to splay open when I bend over and makes the jacket more comfortable.
Bottom line I love the jacket for what it is, a motorcycle jacket. I wouldn't buy a full-weight Aero Front Quarter Horse Hide jacket as a casual jacket. Too heavy, too thick. It would take years of wear before it was comfortable. I might buy a 20 year-old used one though, because after many years of wear, it would be beautiful. So now that I think about it, maybe I would buy one new... a brown one...