6 LEVER padlock Made in USA help with determining an approx. age of this lock

whaleybs

Hi All,
Hoping to get some help to determine an approximate age of this 6 LEVER lock. I’m attaching pics of front and back of lock. Only markings are 6LEVER on the front and Made in USA on the back (this is clearly stamped on the back but didn’t show up well on the picture.)

Thanks in advance.