My grandmas's New Home (Janome now) 531 machine

Question

I just picked up my grandmas's machine to use and I was following the booklet to thread it up right however in the book after the thread goes between the tension disks, it says to then go through the check spring. There is a picture of the check spring protruding from the left hand side of the tension dial, however my machine does not have this 'check spring'.

Does this mean hat my machine will not sew properly? I tried sewing a line and it seems ok but not perfect....i think the bottom thread is a tad bit loose....how do i know when the tension is perfect and is it this check spring that is affecting it? Can i use the machine without this check spring?