I'm not sure about that "M" prefix, but engine serial 5658967 was produced 17-Apr-2003
No model number, model, or engine type is given in the database, but it has this listed:
Description
with rewind starter and starter rope standard
UL-reduction gear box B 2,58
NM - not assembled
with 2 Bing-Carburetors 887823
. . .