chain piecing - two sewing machines going at once - fast!

The machine on the left is a 1957 Singer 1200 in an artisan/dressmaker's table with electric treadle.
It's the same machine as a 201-2 (great-grandma's machine, on the right) except for the knee-operated presser foot lever. 
It's big help in making quick work of sewing pieces together, one after another. (Also called chain piecing. Wheeeeeeeeee)