Say I wanted to be a thief, but still have my car legally registered.
I would want the plate (seven letters) to be the most difficult to remember. No vanity plates.
Actually, I saw a plate the other day that I had a hard time even reading. It was something like, MIWNVNM. That`s what got me thinking about this, not the thief part.
What would be the hardest plate to memorize?
(Mods, if this is not the correct forum, forgive me, or move me.)
Well, first of all, MIWNVNM is a vanity plate…I don’t think any state issues regular plates that are all letters.
Strictly speaking, if you are willing to accept nonsense vanity plates, a plate like MMMMNMM would be a hard one to memorize exactly, partially because it’s just hard to read. The viewer would remember it was a bunch of M’s, but they would probably mistake the N for another M, or forget its position. But as a practical matter, it would be pretty easy for the police to narrow their list down, as there are presumably not too many people with plates that resemble that.
As for truly standard issue plates, I don’t know what to tell you; some are easier than others, but I’d say the batch of “hardest to memorize” probably consists of about 90% of possible combinations. After all, the things that make a plate easy to memorize are things like lots of the same character (MMM-25M), consecutive series (AB-123C), or characters that stand for something familar (911-WTC). Most plates, needless to say, don’t fall into any of those categories.
By the way, I’m told that if you order the vanity plate NONE, you either get no parking tickets (because the DMV sees NONE on the ticket and thinks the cop meant the car had no plate, so they don’t know who to charge) or tons of them (because the DMV sends you every ticket written for a car with no plates). I am not going to be the one to try this experiment 
-Andrew L
AMNESIC
I was in California a few weeks ago, and I found the regular licence plates there very hard to remember. My rental car was something like 4ZY-3Y516, a very awkward combination of letters and numbers. I guess if you’re a local, they’re easier to remember.
Incidentally, does anyone know how the CA plates are allocated? There doesn’t seem to be any obvious age identifier. Do any of the various numbers and letters signify anything or are they just sequential?
But, the hardest one to remember would be unique and thus readily identified. So, not a good choice for a thief.
[sup][sub]This reminds me of a paradox I once heard …[/sub][/sup]
Because of the fonts used in some states, it can difficult to immediately spot the difference between an “I” and a “1”, or between a “0”, an “O”, and even a “D”.
I heard of someone who applied for the vanity plate “I01OID”, but the clerk at the DMV was confused as well and gave him “101010”. (I have a feeling this tale is probably an urban legend…)
My understanding is that CA auto plates run like this:
2AAA000
2AAA001
2AAA002
We just recently passed 5AAA000. What happens when we hit 9ZZZ999, I don’t know.
Our truck plates are like this:
9Z99999
I think our truck plates are in the 6A00000 range right now.
I also think that they define a truck as primarily designed for transporting property and an auto as primarily designed for transporting people. So, an El Camino looks like a car, but it’s a truck. An SUV or mini-van looks like a truck, but it’s a car.
I think that how hard a plate is to memorize depends on the person viewing it. To someone who works with part numbers an all numeric plate is a snap. For example a Mercedes parts guy is used to 12 digit part numbers, therefore 916-473 would be a snap, to an English major, it might present a major hurdle.
CA plates are issued in sequence. Your 4ZY-3Y516 isn’t actually a possible CA license, as they only have 7 digits, so lets change it around to 4ZYY516, which someone probably has (and if you happen to be on the SDMB, please don’t get angry at me for singling you out. Thanks). The next car registered would get 4ZYY517, and so on, just counting up until 4ZYY999, when the next would be 4ZYZ000, and the whole thing keeps on going.
In terms of age identifiers, there are a couple of things. First, the color of the plate tells the age. Currently they are blue lettering on white background, prior to that (the blue on white started in '83 I think), they were yellow on blue, before that it was yellow on black, and I think before that was black on yellow. The other way is just looking at the license number and guessing the age based on that. Obviously, this is more accurate the number in question is close to a number you know the age of. For example, my car ('93) is 3FAKxxx, so if I saw 3FALxxx, I could be pretty sure it was also first registered in CA in '93.
To amplify on what Bearflag70 posted
123 ABC Yellow plate black letters 1956
ABC 123 Blue plate 1963
1ABC 123 Blue about 1968-69 (IIRC)
I know of a case were a car thief took a plate off a couple of year old car and put it on a brand new car that had been stolen. Officer noticed that the car was brand new, but the plate was not. Thief got busted. (In California plates follow the car, except for vanity plates they are never transfered between cars.)
FNORD
calif plates also let you put on one of 4 images…here is the dmv for calif state plate site:
https://vrir.dmv.ca.gov/ipp/ippMain.jsp
Now, I’d like a plate written like that web site address…
I’ve always thought misdirection would be the way to go, substituting I/1, O/0, and so on across a vanity plate. On contemplation, though, computer searching is easy these days; I’d be unsurprised if searching for the “I DO” tag would also search for “1 DO”, “I D0”, “1 D0”, and other possible misinterpretations, automatically.
However, when you get to the standard set of three letters, three numbers (or vice versa), it’s hard to say what’s memorable as it depends in part on the audience. Certain combinations, such as ABC, IBM, 123, or 314 should be pretty easy for most people to remember. But pick any random three letters or three numbers and I bet it’ll mean something to someone. RFC. 218. 402. EAL. They all mean something to someone, and association is the easiest way to remember something.
I think you’re better off perpetrating your crimes in those parts of town demographically inclined towards poor eyesight and lousy memory. But there are already people who take advantage of seniors, so you’d better get in line.
“NONE” is already taken or blocked by DMV.
They do have a neat doohickey for chosing a wording and seeing it on a plate. You first check off the style of plate you want, then off to the lettering.
Actually, the original CA blue plates were “123 ABC”, not “ABC 123”.
cite
Regarding the OP, I once had the idea of making a vanity plate that looked like a non-vanity plate, but had a letter ‘O’ swapped for a ‘0’ or vice versa. So currently, CA has plates formatted as 1ABC234, so you could get the vanity plate 3R0A492, which is readily confused with the valid plate number 3ROA492. This plan could be foiled if 1) cops are too good at spotting the difference between O and 0, or 2) if the software that does license plate lookups is smart enough to check alternates for easily-confused digits (which I bet it is).
wow, after checking out the doohickey gotpasswords posted the link to, I realize that my plan wouldn’t work in california because you can’t choose the character ‘0’ on your personalized plate. You could still do something like “3RJA4O2”, but the limitation makes me think that the software probably doesn’t distinguish at all between 0 and O.
One thing I notices when I was younger is that X’s and K’s can be hard to distinguish on a license plate, especially if you’re reading it fast. This might combine well with the M/N/V combination.
The most difficult license plate to remember is…hmmmm…wait… dang, I had it a second ago and now can’t remember it.
The most difficult license plate to remember?
My own? I have no idea what my plate says, and I’ve had the car for 8 years.
When you request vanity plates in Illinois with a digit in them, the system will offer you the next available digit in sequence if the digit you want is already taken. So, for example, if I requested HOMIE1 and it was taken, I’d get a nice from letter offering me HOMIE2 or HOMIE3, etc.
This makes things difficult if you want to use a digit to make a sound. For example: STR8 UP or 4GET IT depend on the sound of the digit, so if you were offered the next digit in sequence you’d be SOL (becuase 5GET IT just wouldn’t make any sense, would it?). Come to think of it, SOL would make a great vanity plate! 
When I buy my new ride, I’m going to apply for 4SBWTHU (think about it for a moment), which means that if that’s taken, I’ll be offered 5SBWTHU, rather than something else that would work phonetically for that phrase, such as 4SBWITU.
FTR, if neither of those work, I’m going to apply for 10JQKA. 