Oil Pressure Gauge line

[Derm Cain]

Oil pressure gauge on my 1965 230SL has a line from the filter direct to the oil gauge.  The line is in two pieces.  Out of the oil guage the line is steel that connects (with a fitting) to a rubber hose that directly to the filter.  I expect many are the same.  I am trying to determine the metric size of the male and female fittings on the steel line that go into the o/guage and line to the filter.  The size of the steel line may also be helpful.  Any suggestions 

[Derm Cain]

Maybe I need to ask my Oil Gauge pressure line question simpler.  Would anyone know the size of the fittings for the steel line going to the oil pressure gauge on a 1965 MB 230SL?