stm link with number on the shank over "stm"

[bbbouklas]

I recently got an stm link for bari, the owner played it for 40years and 6* is marked on the shank but on the same side with "stm" and exactly over it , not at the bottom of the shank but on the top of the shank!
anyone has ever seen another one like it?

[bbbouklas]

another pic