Scales - MM Close-Up

My grandmother died over 40 years ago.  These kitchen scales sat on her counter for as far back as I can remember into my childhood.  They still work.  I recently weighed a package on them before going the post office and there was only a difference of 1 pound after weighing them at the post office.  The numbers on the scale represent pounds.  As you can see, portions of the face are quite corroded, and I have not tried to clean it.  I haven't been able to locate any markings that would help me look it up to see how old these really are.  Thanks to Skeena to hosting MM again.