Hello everyone! My first post here, apologies if there's bad formatting or bad internet manners

I am looking to purchase a TI-84 Plus CE for the upcoming school year. After looking into the used market - I am on a budget, after all - I noticed that some iterations of the calculator had shiny front plastic and some had abrasive-looking, matte front plastic. I've linked a side-by-side comparison of the two for your reference here (https://ibb.co/djJtWH6). I am aware that hardware revisions M and later of the 84 have upgraded ROM chips (and, if I am not mistaken, a processor as well). Is the case material - specifically the matte/abrasive front plastic - indicative of the upgraded internals at all?
Any response and/or assistance would be greatly appreciated. Thank you!

I'm pretty sure that newer models are matte, while the older models have the glossy finish. You'll want to make sure that the CE you buy isn't the very latest (Buying one from Ebay would be a good option if you buy from a reputable seller), so as to make sure it's not on a newer, locked-down OS version. You can sometimes also tell the age of the calculator by the packaging it's in.

It doesn't have a ROM chip, nor does it have a faster processor, but rather an updated FLASH chip. In any case, matte black is more recent and is a good way to get the recent hardware. You could also look at python variants like the 84+CE Python or the TI-83 Premium CE Edition Python, which will definitely have the latest hardware and the extra coprocessor which doesn't negatively affect performance (at least not in any way that you might notice)
That being said, the easiest and most reliable way to know is obviously by looking at the back and checking the revision, which is the letter at the very end of the serial number (on the CE, it can sometimes be a letter followed by a digit like B0, but none of those will be recent). There have been lots of changes over time which can help you spot different hardware revisions.
This silkscreening will be revision O or later:


If you find one missing the LED next to the USB port, that will be revision T or later:


You might come across some CEs that have weird looking serial numbers like this, in which case, you can know for sure that the calculator has the new hardware because they started doing that around the 40th week of 2019, which is after the switch. If you're curious, you can find out how to break down those serial numbers here.
If you find one that looks like this, let me know

That faceplate to the bottom right looks very weird! Is that on the never revisions or is it a printing eror?

Neither, its a prototype.

I just got a new CE. According to the serial number, it's from Feb 2022, and it has several things that are different from my Dec 2019 CE.
1.) It has a shortcut for the fraction right over the X, T, theta, n button
2.) Right next to the left and right arrows there are blue |> icons, but I haven't figured out what they do yet.
3.) It came loaded with OS 5.7, and they removed all the assembly commands, instead of just disallowing the Asm84CEprogram token, which would make writing ICE pretty hard.
4.) There's probably other differences I haven't discovered yet.

Yep that's the latest silkscreening (first picture of my post)
There are a few places in the OS where those arrows are used like when moving the cursor on the graph screen (2nd + Left or Right will move the cursor 5x farther than just pressing the arrow)
Also in the program editor, pressing 2nd + Left/Right will move the cursor to the beginning/end of the line.
What's the revision and what model of CE is it?

How do I figure out what model it is?

Its written on the front...

It is? Like on the back, such as R-R-TXN-84PLCE would mean it's a model R?

No, the model itself is at the top of the front.

For the revision, it is below what you said, and it can be to the right of the serial number, or within the serial number itself depending on the format.

I just bought a "Mint" TI-84 plus CE this morning at Staples, it has the old silk screening but is revision O - date code is "L-0620O". It has charging LED which is nice.

Recently I found that on the back of the packaging of the newer Ti 84’s on the features list at the bottom the box for ‘save your work’ is checked but on the older models it is not.