[Maarten]

The serial number that should be elsewhere on the back could indicate any rarity and date coding on the various components (picture tube, transformers, semiconductors) will give the approximate build date. Without opening the set, details of the local controls will indicate a rough era.

I don't know Mitsubishi suffixes by heart, but they use them mostly to indicate the destination market. Often two letters. I suspect the M might me for multisystem, for example PAL/SECAM. This might be obvious if we have a look at the local controls or print at the front. There's so much information contained in the set itself.