I always find it interesting for IWC watches with T SWISS T dial appeared on the end 50s’ case serial. Myself have encountered few examples too with original dial/case condition (especially on the Ingenieur 666 reference). My understanding is that the Tritium material only used around early 60s’ era
from my understanding, the jubilee RO were made in different batches and they may be fitted with different crown. In addition, I noticed that the Audemars Piguet near 12 o clock is different among the jubilee edition RO. Perhaps other owner of jubilee RO can shed some light too.