It shows 48A every time, then kicks down to 40A when functioning properly on my home 14-50 NEMA using the gen 1 mobile charger.Assuming there are no more than three potentially relevant "generations" (surely the smallest 3 charger isn't available on any X) you should know the following:
1) The first "generation" had single and dual options, with the single option maxing out at 40A and the dual maxing out at 80A. I think this generation is considered gen2 and was discontinued before the X started being manufactured, but I'm not certain(there was no production pre-facelift X as far as I am aware). Source: Tesla Model S/X GEN2 Charger - openinverter.org wiki
2) The second "generation" (which must be gen3 if that is gen2) had three slots, but two options: 48A or 72A. I don't remember what the option was called (or when/if you even had a choice vs getting the larger option with the 100 and the smaller with the 75).
3) The third "generation" (which may still be gen3, I have no clue) only has one option: 48A.
My 2017 X100D manufactured in June has the 72A charge option. Assuming your MCU shows you 72A capacity for charging when your X is not plugged in, that should pretty much tell you which charger you have. If it shows 48A (or anything else which would likely confirm problems with the onboard charger), you'll need to do a bit more research to figure out what you need to know (i.e. maybe there is a way to tell in the MCU, maybe you can plug the VIN into some site).
Now, as stated above, it appears at 40A, then flips to 24A with no up arrow to increase. I would have expected the car to show a notification of failure or some kind of event that tripped the 50A breaker in the box, but there are no errors in service mode or notifications.
I put in a ticket with service and will go through the process of letting them generate an estimate with PN and hopefully that tells me if it's XS1, 2 or 3 (sounds like 3).
Of course the absolute easiest way would be to simply remove the side panels and look at the charger. I saw it when I had it open last week doing the charging port assembly replacement (coincidental timing that I replaced that due to a sensor error, then this week this happens...), but I'm not sure if the XS#-1 faces in to be visible, or out against the rear bumper corner. Really don't want to have to remove it to see the generation stamping...