Take every catalog with a grain of salt. The variations between countries and regions of every manufacturer from the 60s-80s can we aggravatingly different.

Of things we know, '64 catalog for the Professional is a near perfect fit. I missed it earlier because I misinterpreted the 531 sticker and missed a fork detail, then referenced the catalog with those bad data points. But if the decals and components as-described fit that perfectly to what's in the catalog for '64 Professional, the headset is also a match to (given stack height differences between it and Campy's offerings), unless there's some glaring, obvious error, chances are that's what it is +/- 1yr.