In the early days of the collecting craze, I bought this green Aldens machine. It takes cams, but zig-zags without them. Which is good because I have never found the cams for it.
I find Singer 237's often, and buy them almost as often. This model is zig-zag only (no cams). It's a versatile machine because it can be treadled, hand cranked, or used with the motor it was born with. The 237's were made in Italy.
The Singer 328 zig-zags and takes the standard flat cams. I've got another one in battleship gray. I think they are every bit as retro-stylish as the legendary Singer 500, aka the Rocketeer. The 500 was TOL (top of the line) and this one was a budget model.
I bought my first sewing machine in 1968, a model 348 very similar to this 338. It lasted until 2000 and probably only needed motor maintenance then. Sadly I got rid of it. But now I have a couple of these lovely aqua cam zig-zaggers.
The Singer 347 is another aqua machine which zig-zags, but does not take cams.