On all Nokia phones, specific unique codes are attached to each phone following certain acronyms like RM, RH, RX amongst others.
In the quest to finding the actual (full) meaning of these abbreviations thus, RM, RX, RH and others; many researches have been conducted and all to no avail. What is however common and certain is that, these codes serve one common purpose and significance; maintenance files for each Nokia phones are attached and tagged to the specific code assigned to it.
For Example;
Nokia X2-00 is assigned RM-709,
Nokia 100 is assigned RH-130 and
Nokia N900 is assigned RX-51
Now, if you ever need to upgrade, downgrade or flash either of the Nokia phones above, the required files to carry out the operations are to be found under the specific code above.
Supposing you wish to flash a Nokia N900 using your computer, the files needed to carry out the whole operation are to be found under RX-51 archives.
See here for info on how to download Nokia Flash Files using NaviFirm.
Now, supposing that you want to search for the phone's flash files on Google, you will simply search for "RM files for Nokia X2 or, Nokia X2 RM files."
Identifying Nokia Phones Unique/Assigned Codes: RM, RX or RH
Since the maintenance files for each Nokia phone are contained in the assigned codename archives, it is important to know the codename for each Nokia phone and here, I narrate three (3) different methods you can use to identify or know the codename for every Nokia phone.
1- In the About Phone Section: in all Nokia phones, there is always a section of the phone where you can view the details about the phone. You can simply dial *#0000# from the phone home screen and display the details about the phone.
Either RM, RX, or RH is usually on the first line and is written like either; RM- 709, RH-130 or RX-51
2- On the Phone Battery Seat: the RM, RX or RH of most Nokia phones can also be viewable from the battery seat. When you remove the battery of any Nokia phone, under it, the RM, RX or RH of that phone should be viewable to you.
Note that if the phone's complete case has once been changed, the RM, RX or RH number written there may not be complete for that phone.
3- Google is your Best Friend: In the case that the phone does not boot on and you have a feeling that the phone case has once been changed then, Google is your best friend!
Just make sure that you know the phone's model number and put a search on Google. You may search for Nokia X2 RM number or Nokia N900 RM number.