The primary difference between this switchboard and the one in use in YPD in the mid-70’s is the absecnce of Rotary Dial on the operator’s right. The headsets were also different. Western Electric kept those 500 series switchboards working until well into the 1980’s. The only upgrade was usually the addition of a rotary dial and some time in the late 70’s the addition of tone-tone 12 digit “dials”
It was an adventure and a learning experience for all including the gentlemen from Bell Labs in Moorestown NJ – as a test site for the 557B that was in service for the Telephone Industry (slightly different model than that use in non=TAS offices)

This is a picture of the type of headsets used by both TAS & YPD at that time. Trust me when I say they were damned heavy