Movements - OP IV
The OP IV is Panerai's chronograph movement. It is based on the "high beat" Zenith El Primero.
It is certified with a C.O.S.C. chronometer certificate.
Its characteristic signature marks are small seconds at 9 and a date at 4, central chronograph seconds, and totalisers at 3 and 6.
The variant of this movement used in the original PAM 52 chronograph did not have a date indicator.