I agree on the confusion with regard to the -M and Tender naming. I’ve read the M was a version being used for testing until they get/or got to the final product, the Tender – but it seems to be referred to as the -M more frequently.
I have also seen an article where they said the -M had the same range as the -E. But aside from that one article, everywhere else says they are different – but the length, diameter, etc. seem to be the same. In which case, if the -E and -M have such similar characteristics, how could they have improved the range from the E to the M?…