This reminds me of this item, a Survival kit in a Sardine Tin, a gift I received from one of my lovely daughters (they know that dad likes the outdoors and he often does his exploring all by his lonesome) as a gift:
http://www.amazon.com/Whistle-Creek-Survival-Kit-Sardine/dp/B000O26134
Like a lot of survival tins, it's mostly a very minimal injured-lost-hungry in the wilds kit rather than a riding kit. Still, the list of contents may be helpful to those putting their own tin together:
Acetaminophen, Adhesive Bandage, Alcohol Prep, Antibiotic Ointment, Book Matches, Tea Bag*, Chewing Gun, Compass, Sugar, Whistle, Salt Packet, Energy Nugget**, Duct Tape, Fire Starter Cube, Wire Clip, First Aid Instructions, Fish Hook & Line, Note Paper, Pencil, Razor Blade, Safety Pin, Signal Mirror, Waterproof Bag.
*How to you make the tea? In the tin!
**The Energy Nugget is a fancy name for a small Tootsie Roll. Heh.
It really is a one time use emergency item. The tin opens just like a sardine can, otherwise it's totally sealed. It's designed not to be opened until you really find yourself in deep shit, so all the goodies will still be in there.
Which is why I'm going to be making up a more urban tin like the subject of this thread. First, I gotta get some Altoids.