According to a guy on the 210x/215x Yahoo! group, the "M"
indicates the rig is set up for MARS operation (same rig
as any other 210x, but the band coverage is shifted).

73,
Dean K5DH


In article ,
says...

Recently, I saw (on eBay) an Atlas 210M transceiver. I have owned
210X's in the past but I am not sure what the "M" in the 210 model
number stand for. The unit, at least from the fron panel, looked
exactly like the "X" model.

If you have any info on the "M" model please post.

Thanks and 73's
Chuck
WØCBF