Unexplained MM hooks

I have noticed this same phenomenon on several coins mostly around 1961 [+/- a couple of years] -- A hook at the bottom of the MM [curved facing down].

Does anybody know what causes this and if it has any significance [or variety attraction]?

This particular coin is a LD1960D.


Thanks for any insight into this mystery.

This particular one looks like a die crack. However, there are many where a secondary RPM is seen in/near this position...especially in 1960 and 1961.

I'm with Bob on it looks like a die crack... As Bob mentioned there are those with the secondary MM here is a link to CCs 004 http://www.coppercoins.com/lincoln/d...&die_state=eds with one on the upper serif... Here is CCs 022 http://www.coppercoins.com/lincoln/d...&die_state=mds with a hook off the SE of the MM!!!

One more vote for die crack!