As a general rule that applies to 99% of longsword blades, the name of the swordsmith is on the side that faces out from the body when worn. This obviously differs if the blade is worn edge down (Tachi) or edge up (katana)
Inscriptions of the other side are commonly dates but can include a variety of other things….name of whoever commissioned the blade, dedication to a shrine…..etc etc
However some schools did not necessarily conform to the norm…..just to confuse matters!
EDIT, ignore the above. The post is about tsuba Mei, not sword Mei. Doh!