From their inception the International Time Bureau (BIH) produced records of the deviations between various time sources. I have a sampling of those BIH publications from 1960 in images here https://plus.google.com/photos/112320138481375234766/albums/6078225731350227...
1960 is after the availability of cesium atomic chronometers and during the era when Heure Definitive was UT2. These pages include part of the initial attempt to "coordinate" radio broadcasts between the US NBS station WWV and the UK NPL station MSF. They include time offset plots for various observatories for the entire year of 1960, and a couple of pages of the radio broadcast offsets for the end of the year. Also note that these data were not published until as much as a year after the measurements, and only then could one know what time it should have been.
From the turn of the 20th century it was agreed that everyone would use the same the technical basis for determining civil time, but the quality of time available in any particular place depended on available resources and training, so the implementation was imperfect. In many countries the observatory time was the legal time, and the broadcast time signals were, practically, the official time. Plowing through these historic records of time offsets only makes sense for projects such as re-reducing occultation data.
The tz database has always eschewed sub-second offsets. The data on these pages show part of why that is a good thing. -- Steve Allen <sla@ucolick.org> WGS-84 (GPS) UCO/Lick Observatory--ISB Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m