Or they always used a good quality oil, it leaves next to nothing on machines that haven't been used that much. Most zigzaggers are made to lift or unscrew the top. Oil or grease matters, either has a drawbacks but their advantages. The only disadvantage with oil is more frequent applications, and in some cases you can't afford the cance of over oiling; since it looks like the motor is in the back it's less of a problem. Bernina gears are mostly oiled, much the same with Elna and German models. Singer had a few grease points on their zigzaggers. Your Montgomery sounds like a very promising machine, have you had a chance to get to know it?