I was looking for a set of playing cards with numbers instead of the usual faces. Ideally marked, but was willing to mark them myself. Very surprised that there seems to be [almost] NO numbered decks out there to buy. I found some on Amazon(very cheap), but they were bridge size, and really plasticky feel. So awful to handle, I threw them in the bin.
I was planning to buy some blank cards & write my own numbers. Then stumbled on the CIPHER DECK.

They are poker sized, and printed on nice card stock.
The numbers are nice and big, including the indices. The 6 and 9 are underlined to avoid confusion. (Not strictly necessary because the indices make the cards different - but a nice touch).
The pattern on the back is unlike most decks I am used to. A fairly simple geometrical pattern. It only seems to be available in one colour - blue). I don't think the backs would generate suspicion, because it is an unusual deck anyway.

The marking system is a simple code. It is not a "reader" deck with actual digits. I like this because the problem with readers is that the human brain recognises symbols so easily. This means the marks are usually tiny to avoid being noticed by spectators.
The marks are in a location which most magicians would probably agree is most useful (can be seen in a spread).
The system is simple, yet ingenious. Easy to read if you know it, but otherwise not too obvious. The kind of idea that makes you say, why didn't someone think of that before?

BUT it could have been designed a lot better with just a bit more thought.
There are several weaknesses -
1. the zero's and 5's are much more obvious than they need to be. This could easily have been camouflaged by incorporating some similar patterns into the rest of the back design.
2. there is an extra card with 65 on the face. I haven't accessed the online tricks yet, but presumably this "stranger" card is used in some of them? This card is NOT marked, and could not be with the system they have created - which could only go up to 59. It would have been so easy to make a marking system with a greater range (eg 99).
3. the deck would fail a riffle test (like most marked decks). It would have been easy to make the whole design flicker by randomising the back design - like DMC Elites. Of course this does not mean they would "pass" the test. But it would disguise the specific location of the markings,

The deck cost about $35, which I think is a lot of money for a deck (even a gaffed one).

OVERALL -
They definitely met my requirements, and I do recommend them. But the marking system could be improved, and they are rather pricey!

PS. The marking system has potential for use with regular cards too. Obviously it could be used with stack numbers. But could also be adapted to suit & rank. It would be a bit too obvious for a lot of magicians (and of course not Bikes) - but is very easy to read!

PPS as well as the 65 card, there is a double-backer, and a double-facer (37/24). No jokers.

I've played around with these a bit more and discovered another issue.
The patterns for the first digit are different from the patterns for the second digit. This means your brain has to work much harder to read each 2-digit number.