VINTAGE REGENT 555 BASEBALL GLOVE RHT BOBBY SHANTZ MODEL SANDY KOUFAX SIGNED?

Description

the model is a BOBBY SHANTZ, diminutive lefty who had considerable MLB success
THIS IS A VINTAGE REGENT #555 fielder's baseball glove 10" right hand throw POSSIBLY SIGNED BY SANDY KOUFAX, SIGNATURE IS UNAUTHENTICATED. (read on)
condition is ok, has several broken laces but leather is pretty good
item is as we purchased it, we have not cleaned or tried to repair laces, etc.
we purchased this glove at an estate sale near the Chicago area from a baseball loving family
the "SANDY KOUFAX" appears on the thumb of the glove and was obviously written some time ago, as it is faded and not terribly clear, could have been written by a friend, looks somewhat like adult signature
comparing the signature on line to Sandy's signature some look similar, others have notable differences
the owner of the 60's era glove and  his father are both deceased, son loved baseball-played some college ball
this glove is from a era when you could go to Wrigley Field and players would spend maybe half an hour before games signing items the fans brought to them
perhaps when the Cubs played the Dodgers???
upon first glance at this glove my baseball fan wife and I both said "Sandy Koufax"??
we are not claiming this is truly an authentic autograph but there is some possibility due to the signature location and age, Wrigley proximity, owners' love of the game
we have made no effort to obtain authentication, nor plan to do so-NOT CLAIMING THIS IS AUTHENTIC SIGNATURE-DO NOT KNOW
what do you think??