To remove the mic completely, the connector must be unsoldered and the switch tip removed. Once inside, we see something that looks like the Easter Island statues!
The ribbon is hiding behind the baffles, and the motor requires quite a lot of disassembly before the ribbon can be accessed. The ribbon itself is about 1.8 mm wide, so a bit fiddly to fit. Like most mics of a certain age, half the problem is that the ribbon has become oxidised and stiff, and the other half is small particles of wild iron that that have become stuck between the pole pieces, preventing the ribbon from moving freely.
Removing the strong magnets made cleaning and re-ribboning a lot easier! The transformer and filter inductor are housed in a mumetal can, screwed beneath the motor assembly and above the filter switch.
As usual, the mic sounds best without the high pass filter engaged, although I can imagine it being useful to compensate for proximity effect when close micing some instruments.
There doesn’t seem to be much information about this mic available on-line, but I have scanned an old Melodium catalog featuring the RM6. There is also a French language review of the RM6 over at Audio Fanzine. They seemed to like it, and gave the mic 9 out of 10!