HP48

[Steve Simpkin]

It has something very similar. The closest operation to "Last X" is probably the CMD keyboard command. Depending on the HP-48 model, it will either return the last argument(s) you had on the command line or a pop-up window with the last 4 command lines.

For example, if you add two numbers together like this:
1
Enter
2
+

It returns the result 3 to the stack.

Pressing the left-shift CMD key on a HP-48-S/SX will return a 2 to the command line. You could then press the - operator to subtract it from the result and undo the calculation, similar to how you could use Last X.

The ARG keyboard command (aka LASTARG) places the arguments of the most recently executed command to the stack so you can use them again. In the above example pressing left-shift ARG key after the addition would return a 1 and a 2 to the stack (the 3 would still be present be on stack level 3). Note these commands are on different keys on the HP-48G/GX series.