My Metal Brain...

I went to Michaels Craft Store and bought a cool little tin a while ago. Had no immediate use for it so it sat for a while till I found it was pretty much the perfect size for an improved Hipster PDA.
The tin is 81mm wide, 127mm high, and 18mm deep. I guess that makes it technically something like a 3" x 5" tin (see where I am going here?)

So, after a little visualisation of what I wanted to use it for, and what tools I might need, here's what I did.
1...Cut a slot for the mini-binder-clip to pass through (Dremel and parting disk, Round file, a burnishing mop in the Dremel to smooth the edges. Since I removed a little of the plating and paint, I then painted the machined edges with clear Nail Polish to prevent corrosion.
2...Made a mini-bungy to hold the bottom of the 3x5 card down using white 1/8" elastic and a short length of 5/32" inside diameter Aluminum tubing. Crimps using an electrictal crimper-stripper hold the ends rock solid.
3...Cut some index divider cards out of 3x5 card. I reinforced the tabs with scotch tape. Corners are all rounded using an excellent paper/card "Corner-Rounder"....about $2.50, shipped from China. The same Corner-Rounder rounds all the corners on the 3x5 cards too (not strictly necessary, but aesthetically pleasing).
4...Assemble everything. The rounded corners look especially sharp as the radius matches closely the tin corner radius closely. Even the Binder Clip matches the purple stripe on the tin face!
5...Lastly, the real kicker...the 3x5 cards fit perfectly into the recess of the rolled-bottom of the tin when a small amount (18mm) is trimmed off of one long end to fit perfectly. I use the 3x5 cards that Staples sells: they are "Portrait-Ruled" on one side, blank on the other. That way I have not one, but two perfectly flat and accessible surfaces to write on at the same time....one for "Calendar", the other "Notes", or one for "To-Do" and the other for "Information"...the possibilities are endless.
Other good things with this design...it's extremely pocket-able, just a couple of millimeters larger than a 3x5 card...as a right-hander, my righthand protects the binder clip extension from any snagging on a pocket when I insert it, or, more importantly pull it out...there's ample space inside the tin for a small pen, and a Tyvek Wallet holding a few Credit Cards and some cash...or a ThumbDrive...endless choice in what's a combination of a HipsterPDA, a small wallet, a repository for small bits and pieces that you don't want to have getting crumpled in the bottom of your pocket, and a great protector of notes and sketches.
Lastly, the final pic shows how easy it is to "extract" a card from the bottom of the tin. Getting it in to the slot is very easy too...just put a slight flex in it and release.