Premise: We’ve got a time machine that can send one item exactly 1000 years into the past. This item must not have any writing on it, print out writing or even display writing or pictures. It can be mechanical in nature, must be fully assembled and it must fit into a symmetrical 8 cubic foot box(2x2x2).
What would you send back, and what do you hope would be the result?
Just “into the past” or “1000 years into the past at a specified location?”
Any location you choose.
Does a globe with just national borders count as a picture?
I’d say so.
A loaded revolver and box off cartridges.
By accelerating the invention of the revolver by 500 years, many ripple effects will have certainly taken place by now.
A film camera.
One fully assembled item. I’ll allow the loaded revolver.
To what intent? It’s a box that might have recognizable buttons on it, but even if they figured out how to point and shoot with it, eventually one of them would find the switch that opens the film compartment, and it’s extremely unlikely they’d do it in the dark. So they’d have ruined film, at best, and be no closer to understanding why you sent it.
On the other hand, there’s some merit in just toying with them. So I’d send a smaller version of the time machine!
My first thought was to send a functioning windup clock (with no numbers on the face) for ocean faring navigational purposes but I doubt that would change things very much. What they had was probably good enough for their purposes.
So I’d send back a box of corn to anywhere in Europe. Having an additional grain that wouldn’t be susceptible to the same diseases as wheat and potatoes might help out with a few of the famines.
I also thought about breaking a baby horse’s legs and cramming it inside a North American box but you really need at least two horses to make any lasting effect.
While we’re at it, do biological elements count as “single items?” That box size is just large enough you could send a sufficiently contortionist small human.
No live(or formerly live) items, please. Remember: 2ft x 2ft x 2ft box.
You know, SkaldCo time machines don’t come with all these limitations, although there is something in the contract about my firstborn.
Because the idea of sending something with the capability to produce a picture that will not produce a picture for them amuses me. And who knows, maybe playing with it would help give someone a lightbulb moment.
With the restrictions of no writing and no pictures, we’re limited to things that they could conceivably create on their own or things they pretty much can’t understand and will probably be lost or destroyed before sufficient advancements can be made to understand. So we might as well amuse ourselves. Or so it seems to me.
Incandescent bulb, carbon and lead battery flashlight
Small internal combustion engine with pull-rope starter and as much fuel as possible - it’s going to take them time to figure out oil and how to refine it.
Steam engine with kindling in the firebox - that should give them the idea to build a fire there. Yes, with water in the boiler. They could scale it up with just a bit of improvement in their metals.
I’d be inclined to ship these to either China or the largest Muslim empire of the time - they had the technology to exploit them. The flashlight could go to them or wherever in Europe it’d be safe from the Church, which would condemn any/all of them as Satanic and ordered them destroyed.
The RCC really acted badly toward science back in the day.
One thing would be safe anywhere, as lng as it fell into sea-going hands: A globe showing land masses - and the western hemisphere - the improvement in there maps would be a huge boon to commerce, and the existence of the Americas would set off a rush - maybe the Spanish and Portuguese wouldn’t get a lock.
Come to think of it, scratch the idea of sending the globe to Christian areas - they behaved rather badly toward the natives largely due to their religion. China scores another. Don’t know if Islam would be nicer - there are some serious loons in that religion too.
A nice, large tin of food - and no can opener. 
Exactly 1000 years? Canute was proclaimed King of England in 1014. Maybe he could use a pair of galoshes.
A Tonka grader/dump truck for the preColumbian N.A. tribes. (You would have to paint out the logo, of course.)
A microscope. Or a telescope.
The shoes I’m wearing right now.
Longstoryshort, i do not like to try on shoes. I find ones I like in my size, pay and go. These shoes were on sale, looked nice, but I’ve grown to hate them. They are awkward to wear (the shoe is designed to rock like a rocking chair). My gf finds my shoe purchasing behavior maddening. I am too frugal to just throw the shoes away, so for the last year (they are made well, I’ll give them that) I have just been suffering in silence.