Google has been of limited help. How they are made is my first question. The only information in Googlespace seems to be that some have the hologram printed in a resin layer over the real coin, and some have it in the metal. How do you get a fine interference pattern stamped onto the coin? Or is it not part of the die, but etched on afterward? Is the process high technology, or just vanilla? How good are they? Are the holograms as lame as the one on my Visa card, or do they give a full 3-D effect? What do collectors think of them? They don't seem to have much mindshare. Are they considered a vulgar gimmick to be despised (like colorized coins), an interesting but obscure niche, or just not thought about at all? The answer I'm hoping for most is to be told there's a good book covering the subject. That's better than taking up everybody's time here. But seeing what people think in a discussion would be fun too.
I have an (I believe) 50 Yuan piece with a hologram on the revese. I think it's kind of a neat safety feature myself. (I'd post pics, but my photographing abilities are on par with my camera: nil.
Both types of "holograms" can be found on coins. No they are not the true 3-D type of holograms that you create with lasers. The printed on label type is a lot like the ones on the credit card. I find the ones that are created as part of the striking of the coin to be more interesting. It must be difficult to design the different complex shapes so that the light catching different facets of the metal as the coin is tipped back and forth create the different images.
I've found out a little more, and it seems to be on the high-tech side. It starts with using an electron beam to etch a pattern, finer than a photographic process could produce, into a special material ("electron beam lithography"). Nickel gets plated or somehow deposited onto the master, to create a nickel shim. Then the nickel piece gets pressed into the coin surface. Since it's called a shim, I'm guessing it's put over the regular die. I'm fascinated that you can transfer detail that fine onto normal metal during a striking process. How long do you suppose the shim lasts before it wears out?
That is very interesting information. I had been wondering that myself. Most people do seem to ignore them. I don't have any myself but if I see a design I must have, I will get it. Holograms were very popular in the mid 1990s and then seemed to fade away from popularity, I've always found them kind of cool. I can't imagine how diffacult it must be to make it part of the coin design. I have to say...I'm impressed!
I got more impressed when I read the Wikipedia article about electron-beam lithography. A lot of the article requires college-level physics, but some highlights are that it can create features 1/20th the size of a wavelength of light, exposures can take days, and to really do it right you should be using a four million dollar machine. The "cheap" way to do it is to start with an electron microscope and add a $100K accessory.
The Royal Australian Mint has something awesome about Hologram coins. I have taken some pictures which you may find it interesting: http://www.gxseries.com/gallery/index.php?display=Canberra Mint07/mint58.jpg There should be about 6 pictures or so related to hologram coins so do give a look.
GREAT information! Thank you very much. It answered one of my outstanding questions, which is how long the nickel shim lasts (15 coins), and is the single best overview of the process I've seen in one place. Now if I could just figure out how they electroplate nickel onto nonconductive plastic ...
Holographic colors with a bit of early toning. The hologram is etched into the die therefore stamped into the silver. Z
