Hi everyone - I just stumbled over this forum and wanted to offer my 2 cents, as I've been scouring the internet for vintage sewing machine info in the last couple of days and as I've always had a soft spot for these Singer clones.
Singer 15-clones (and indeed "proper" Singer 15s, as J Miler pointed out) have been made in India and in China since at least the 1940s/1950s and are still produced in innumerable factories. In China, they are known as "JA" domestic sewing machines. The JA-1 is the basic model, the JA-2 has reverse and the JA2-2 adds a cloth feed regulator.
One of the more known (and the original, I gather) Chinese factories is Butterfly in Shanghai - this is the reason why they are often generically referred to as "Butterflys". They are, however, sold with an amazing number of brand names (and you can probably have your own put on them, if you order a few). As noted, they exist in hand crank, treadle and electrified versions and are quite popular in Africa and in places around Asia, where their cheap price, "human power" and time-tested design are valued highly
