All you need for this modification are business cards, mint tins, a fine half round file and tin snips.
Step 1: Argh! Just a Little Too Tight.
This shot shows that the rounded and rolled corners of the tin make the fit going in and out too tight.
Step 2: File the Corners
First, file the front two corners down through the rolled edge.
Step 3: Corner After Filing
This is what the corner looks like after filing it down.
Step 4: Snip the Edges
You could do all of this with the file, but that would be too tedious. Use the tin snips to cut down the sharp tail left by filing. Finish it out by filing all the edges smooth. Repeat for the other corner of the tin.
Step 5: Finished Front Corners
This is what the tin looks like with the front corners look like at this stage. Loading the cards is easy enough now. I suppose you could stop here and use it to carry your cards, but getting one out easily will be a challenge. In the next few steps we'll add a mod to make it easier to pick up a card.
Step 6: Find the Center
I marked the center, and lines to layout all of the areas I wanted to cut out. You don't have to. You can just wing it.
Step 7: Cut Out a Notch
Cut out an opening. I think it's easier to do it in stages. The tin distorts less. Be sure to leave the catches for the lid.
Step 9: Finish the Opening
Finish the opening by filing and getting rid of the sharp edges.
Step 10: Guess What - You're Done!
Done. Load your cards, and take the tin with you to promote yourself.