Coot 0.5 doesn't support old pdb format and cannot add element column. m2.pdb is old format, so you must convert it.
for example pdbset XYZIN m2.pdb XYZOUT m2-pdbset.pdb <<eof cell 100 100 100 90 90 90 spacegroup p1 eof I attach the converted file, and it shows well in C-alpha.
m2-pdbset.pdb
Description: Protein Databank data