Those sneaky devils at Topps have added two unannounced mini insert sets into 2007 Allen & Ginter. Like the Flags of All Nations insert set, Topps has created two more tributes to the original A&G non-sports sets. The unannounced sets appear to be 'sets that never were' that mimic the style and subject matter of the original A&Gs while the Flags set is based on the original N10 set from Allen & Ginter. Topps didn't include these sets in the checklist inserted into each box, so I have compiled these checklists from current eBay auction listings for reference.
The first set is Roman Emperors. I haven't seen any confirmed odds but looking through a few case breaks on the forums they seem to be inserted 6 per case, or 1 every 2 boxes or so.
E1 Julius Caesar
E2 Caesar Augustus
E9 Marcus Aurilius
E10 Septimus Severus
The second set is Deadliest Snakes. This set is inserted 1 card per case or 1 in every 288 packs.
S1 Coral Snake
S3 Black Mamba
S4 King Cobra
Assuming the Emperor's pull rate is actually 1 in 48 packs here are the odds of pulling any individual card from a pack, or how many packs it would take to get a complete set with perfect collation and no doubles.
Flags : 50 cards inserted one in 12 packs = one in 600 packs
Emperors: 10 cards inserted one in 48 packs = one in 480 packs
Snakes: 5 card inserted one in 288 packs = one in 1440 packs
Basically, if you are simply looking for a type card so you can say you have one of each type of card, Flags are the easiest. However, if you are going to try to complete the set the Emperor cards are just a little bit easier to complete. Snakes are just plain tough all around.
Emperors may only be 5 per case, I've seen both 5 per and 6 per listed on various forums. Packing out at exactly 5 per case would be a probability of 1 card per 57.6 packs, which is not exactly a usual ratio. It is probably somewhere in between which would account for why some cases have 5 and some have 6.
Also, while searching for mini cards on eBay, I have found several auctions that have individual Flag cards listed as SPs within a lot. So far I have only seen a few, and I haven't seen any rhyme or reason for the SP designation, but there may very well be short print flags floating out there as well. If that is the case, then forget about having an easy time finishing that set.
Bottom line is, see all those odds up there? Forget about them. They are completely useless. Right now the only thing sure is that Snakes are 1 a case. I'll continue to update If I find anything concrete on all this, but since we're still waiting on an official SP list for Topps, who knows when that will be.