G'day, if you look around, 2x2 come with holes in 2.5mm increments, from 17.5 to 37.5 mm. I've also seem in 39mm, for Crowns & similar, but that's the biggest opening that I've seen. And, at that size, the structure seems a bit flimsy. Everything smaller is fine.
I've found that thick coins don't fit into the size you might expect, and I have to go up one increment.
If you use 2x2, you'd be well-advised to look out for a "flat-clinch stapler" to close them with. I had to hunt around, but I found one for less than $10 in a good stationers.
The albums are great for display: generally, 20 pockets per page.
You can also get smaller "wallets" with six pockets per page: great for taking a few coins to a meeting.
For coins that you want to store, rather than display, I found that well-know brand of tackle-box, manufactured in Illinois, has a model that holds 2x2 just perfectly, with the lid closed. These are robust, and I can stack a few boxes on top of one another.
There are other options for 2x2 storage, but the important thing is to get your coins into the holder, to protect them from drops, bumps, etc.
Peter in Oz
"the only people who are not confused are those who are not paying attention."
Edited by Peter THOMAS
03/30/2008 11:38 pm