I got my sample today, thanks. Only 5 days to cross the Atlantic via snail mail !
I aggree with enmaku: the "see through" weakness is serious and was clearly identified by Bitbills when they first came out. You want to double the metal hologram sticker with one on the back. I remember the Bitbills guy explaining how he had tested an electronic microscope in its "see through" capacity. Only a dual metal layer can mitigate the risk albeit not entirely.
Right, I thought having a full key would cut down the risk, but not so much. Every check will now have stickers on the back as well. Right now I only have scratch off stickers, but the ones on the back will be replaced by standard non-scratch off holograms in due time.
The full key checks (R1s) will still be available, but by request only, Because nobody wants to type a key that long...
Yep, I went through the same consideration. It is way too easy to see through the paper on the reverse side with a bright light, and so I do holograms on both sides.
Be careful with scratch off stickers. I found that most were removable from the glue layer by applying a little warmth. My first tries were with them, and I was able to successfully take off the scratch off sticker and then re-apply without any issue.
I am currently using these stickers:
http://www.ebay.com/sch/i.html?_trksid=p5197.m570.l1313&_nkw=Hologram+Label+Tamper+Evident+25mm+square&_sacat=0They are not outstanding, but they do a good job of falling to pieces when you try to remove them. I put a small white square of paper over the qr code for the private key to prevent the hologram from remaining on the actual code.
The downside is that as you can see they are easy to purchase and replace by the hacker.
If you want to go hard core, contact casascius,
https://bitcointalksearch.org/user/casascius-2676. He has been working with a company on custom holograms that he could be the central provider of that would have a thermal overprint of your company name. This would be very difficult to forge, and so would prevent the problem of a user scraping off the private key cover and then replacing it with a brand new sticker.
Since double stickering means doubling the costs of holograms, you will realize that this gets expensive fast, and in fact making coins and single stickering is cheaper. You might want to consider this route, and again casascius it the man to talk to. It turns out that coins are cheaper to make than holograms, and people like them more, so it is a win-win. If I sold more of my stock, I probably would go down that route as well, but I really don't sell enough to invest in the bulk order of coins. You may also want to look at plastic cards. They can look good, and if you make them thick enough, and dark enough on the reverse, the private key might not be able to be viewed (experimentation needed here).
In any case, good luck! I would love to see more people making physical forms for passing bitcoins along. One of the problems bitcoin has regarding street-corner purchasing is its need for network access and the lengthy amount of time for a transaction to be recorded (I curse satoshi ever time I am trying to give someone bitcoins and we end up twiddling our thumbs for 10 minutes waiting). It also has the nice side effect of transactions being even more anonymous as they happen outside of the blockchain.
I expect that one day when bitcoin becomes a common currency for transaction, there will be many styles of bills, coins, and cards floating about much like the days before the central banks where currency was being printed on a local level.
What exciting times.
