Unstable is a small set with 60 commons, 60 uncommons, 35 rares, 10 mythic rares, 45 contraptions, five basic lands, and one special black-bordered card. Some of the cards have multiple variations. The number of rares and mythic rares is the same as small sets prior to Oath of the Gatewatch, but smaller than contemporary small sets. Foil cards are included in booster packs with advertised odds of 1 : 67 cards. The set was printed in the USA.
Unstable was sold in 15 card booster packs (which contain an additional token card). Booster boxes have 36 packs.
Unstable uses sequential collation. The runs tend to have 50 cards. I theorize that this reflects the use of 10 × 10 sheets divided into top and bottom halves. The unusual sheet size may be related to gutter cutting, a manufacturing technique that allows card art to extend to the edge of the card. 
Packs have back-facing cards with 8 commons, 3 uncommons, a rare, a basic land, 2 contraptions, and a token card. If there is a foil, it will displace a common. Foils can appear in two different positions. Foil commons, uncommons, and basic lands appear between the uncommons and the rare. Foil contraptions and rares (possibly excluding Steamflogger Boss) appear between the land and contraptions. If Steamflogger Boss appears, it will replace the basic land slot, not the rare slot.
|8 Commons||3 Uncommons||1 Rare||1 Land||2 Contraptions||1 Token|
|8 Commons||3 Uncommons||1 Foil||1 Rare||1 Land||2 Contraptions||1 Token|
|8 Commons||3 Uncommons||1 Rare||1 Land||1 Foil||2 Contraptions||1 Token|
There are four common runs: A, B, C1, and C2. Half of packs have A-B-C1, and half have A-B-C2. Runs A and B each have 25 distinct cards. There cards in these runs are repeated twice to give length 50 runs. There is some overlap between runs C1 and C2, but C1 has a length of 50, and C2 has length 32. Between these two runs, all the commons with multiple variations appear with each variation repeated twice. The few additional cards in the run are each repeated eight times. For these purposes, Curious Killbot, Delighted Killbot, Despondent Killbot, and Enraged Killbot are treated as four variations of the same card.
It is possible that A and B are printed on the top and bottom halves of the same sheet and C1 and C2 are pritned on the top and bottom halves of another sheet. These sheets would be printed in an 4 : 1 ratio to ensure all cards are equally common (although Secret Base which has five variations instead of four is in some sense overprinted).
C1 packs have 3-4 A cards, 3-4 B cards, and 1-2 C1 cards. This means packs can be 4-3-1, 3-4-1, or 3-3-2. C2 packs have 3-4 A cards, 3-4 B cards, and always 1 C2 card. So, C2 packs can be 4-3-1, and 3-4-1. In some boxes, A and B are reversed with B cards appearing first, followed by A cards. (Hence, the A and B labels are arbitrary.)
When a foil appears in a pack, it will displace a common card. My information here is probably incomplete, but I believe foil commons and uncommons appear in C2 packs and displace a common of whichever of A or B is first in the pack, and foil contraptions and rares appear in C1 packs and displace a common of whichever of A or B is second in the pack. I'm not sure about foil lands (or Steamflogger Boss). I think that nothing displaces C commons. There is also some evidence that the foil commons with variations are printed on a different sheet than the other foil commons.
There are three uncommon runs: A, B, and C. Run A has 10 distinct cards including the three uncommons that have 6 variations. It's possible that A is further split into A1 and A2, but I don't have enough information yet. Runs B and C each have 25 distinct cards each appearing twice. Packs can either have one of each, or no A cards with an extra B or C. A always appears first. B and C can appear in either order (independently of the common A and B order), but the order will be consistent within the same box. Mathematically, A cards should appear exact half of packs. This bears out empirically.
There are probably three contraption runs: a common run, an uncommon run, and a rare run. (I haven't calculated the rare run yet, so it is a little bit uncertain, but the sheet math works out well.) The common run contains 10 common contraptions each five times. The uncommon run contains all 15 uncommon contraptions each repeated twice plus the remaining 5 common contraptions each repeated four times. I speculate that the rare run contains each rare contraption four times and each mythic rare contraption twice (which gives another 50 card run). The first contraption in the pack will be from the rare run or uncommon run. The second contraption will be from the common run, or if the first contraption was rare, it may be from the uncommon run. Rares appear 2/5 of the time. Contraptions from the uncommon run appear the other 3/5 of the time in the first slot plus half the time there is a rare in the first slot for a total of 4/5. This means that commons from the uncommon run are 4/5 short-printed compared to other common contraptions.
There are 10 foil tokens and 10 non-foil tokens. These are assumed to be printed on two different sheets. Each set of tokens has its own 10 card sequence, and these sequences alternate. So, it appears that all 20 tokens are equally rare.
The A common run consists of 25 different cards each appearing twice. These cards are white, blue, and green. The choice of first card is mostly arbitrary.
The B common run consists of 25 different cards each appearing twice. These cards are mostly black and red.
The C1 common run contains cards that have multiple variations and colorless cards. Between C1 and C2, each variation occurs twice, and each other card appears eight times.
The C2 common run contains cards that have multiple variations and colorless cards. Between C1 and C2, each variation occurs twice, and each other card appears eight times.
The B uncommon run consists of 25 different cards each appearing twice. The choice of first card is mostly arbitrary.
The C uncommon run also consists of 25 different cards each appearing twice. The choice of first card is mostly arbitrary.
The common contraption run consists of 10 different cards each appearing five times.
The uncommon contraption run consists of 15 uncommon contraption cards each appearing twice plus 5 common contraption cards each appearing four times.
 Mark Rosewater talks about gutter cutting in his Drive to Work podcast #492 "Printing."