BSA Folding Bicycle

[horsa]

Actually my mistake after looking at your photo again. I didn't notice that the post the saddle is mounted onto is pulled out of the frame support. At first glance, it looked like it was one of the first pattern frames. They welded the short pipe the saddle sits onto the front of the upright frame support. The second pattern has the short piece of pipe necked down to fit inside of the upright frame support like you find on most modern bikes.