On my 60, the headstock sight glass required eye torture in order to see oil moving.
We "know" the line that shows oil movement doesn't fill the sight glass; it just gives a steady drip. I say "we know" this a bit loosely, since I'm basing it off of all threads I've been able to find on this subject. Many hours spent!
Anyway...I became tired of how difficult it was to see this drip, so just last week I tried some pipe cleaner. Just a 1" length, ends finely crimped over and loose hairs removed. It sticks out of the oil line just enough to bring the drip line outward, away from the oil level plate and up against the back of the sight glass. WAY better view, noticeable at first glance.
Now, the drip itself doesn't fill the glass. But that may not necessarily mean the glass is/was not supposed to show an actual level, also. I remember finding a comment made years ago here on PM where the poster said something about the FRONT headstock sight glass originally being "vented", allowing an actual level to form. By accident I realized this works, after so many times I removed/installed the sight glass while the spindle was running. If I notch the top of the gasket and leave the top screw a little loose, the glass fills to 1/4 level at lower spindle speeds, and up to the level (middle) mark at top speed. You can see this is separate from the "pump is working" metered line when you run the headstock with the glass off.