These old sewing machines are nearly indestructible. Take this cast iron Dressmaker 650. I could probably run over this thing with my 6,600 pound Ford F250 4x4 and it would still work. Little bits might snap off or bend and it wouldn't look pretty but it is so beefy that it would probably still work.
I just got done cleaning and oiling this one. It works as well now as the day it was made. Simple controls, easy to use, straight and zig zag. It will sew through 8 layers of denim like it wasn't there. Ok, so maybe it knows it's there but it doesn't break a sweat doing it.
This machine takes high shank feet, which usually gives me an indication that it was meant for a little heavier duty usage than a machine with low shank feet. I don't know if that's true or not, but that's my thinking. Here are a few more photos.
The shuttle hook carrier assembly translates left and right with the needle when doing zig zag stitches. I think this is a better setup than the fixed hook carrier that front loading machines have.
Four layers of denim. Nice looking stitches.