Just took shipment of a 1949 (I think) Corona Silent and found, while setting the tabs, that the tabulator scale is two spaces off from the front scale. On the far right of the tabulator scale bar is a screw that I thought would adjust the scale's position (there is a spring there), but I can't make it move. I'm not sure if the screw is stuck after 67 years or if there is another way to adjust it. 

How do I adjust this and is there a preferred way of dealing with a stuck screw like that? 

Thanks for helping out a newbie.