The brass lamp with the large, green, glass (plastic?) shade is all but ubiquitous in traditional financial institutions. What’s the story behind this practice? It can’t be so simple as that green goes well with those big, expensive, mahogany banker’s desks, can it? 
I don’t have an answer, but I wanted to say I was surprised to see that the Google Image Search gives an amazingly uniform result when queried.
I guess the rebel account manager could pick up one of these puppies to showcase his individuality 
I’ve always wondered this too and was really hoping I’d hop into this thread and see the answer! There is very little information out there about the lamps as far as I can see. Good question though. I hope someone knows!
Sometimes, you see a money-counter type wearing a translucent green visor. Like in a TV show where there is some seedy back-room gambling operation, the guy who is actually counting the money wears the visor. I have no idea why.
But the lamp and the visor are both green. Are they related?
WAG, the green shades serve as filters and aid in easing the eye strain from squinting at columns of tiny numbers for hours at a time?
Might work for the poker-style eyeshade (you’ll also see them on poker players in a lot of old movies), but the banker’s lamp points a regular incandescent bulb at the desk. The green is just on the outside.
Oh, and to slightly nitpick the OP, I think they might be porcelain.
I know that there was a popular expression at least ten years ago for people in accounting and realted professions: “green eyeshade.” Some congressmen who were seen as overly concerned about balancing the federal budget were called green-eyeshade republicans.
Maybe just because they work effectively?
I’ve used one, and it really does function quite well as a task light. The light shines quite well on the paperwork on your desk, and the green shade on the top keeps the light from glaring in your eyes. And the shade can be rotated a bit to aim it right onto your work. The big base makes it pretty stable, and can hold pens, pencils, etc.
Plus, since the design has been around for quite a while, it’s a fairly cheap light.
Likely it is the same story behind accountants green visor eyeshades. 
But they both offer the same benefit in that they place a filter between your eyes and a point source of light, so that only softer, reflected light reaches your eyes, from the area that you’re concerned with.
Related question:
What’s with the armbands you always see on the stereotypical “banker”? They don’t seem to be holding up anything, the long sleeves sit where they usually would.
Arm garters keep your sleeves from sagging when you are sitting down. Your shirt is cut for a certain arm length, usually arms at sides. If you reach above your head, your sleeves are too short. If you are sitting down working at a desk, your sleeves will usually be too long. Add into that the fact that for the longest time, shirts didn’t have “custom” sleeve lengths…you got what everybody else got, and unless your wife was a seamstress, your sleeves were probably a mite long. The arm garters keep your sleeves at a desired length, free from getting in your way and dipping into the inkwell.
I’ve asked about the green eyeshades before, and no one could give me a good answer. All I found with Google was people asking the same question.
Why would green semi-transparent material make for a good eyeshade? Why let so much light through, and why green?