[exador]

Presumably Paul Altieri

It continues to be a point of debate within the collecting community. While certain letters from Rolex state that "to the best of their knowledge" a blue insert was never officially offered, there also exist service quotes for 1675 watches from Rolex that explicitly mention the all-blue insert.
Some explain this discrepancy by drawing the distinction between factory-fitted components and genuine service replacement parts. It is confirmed that the all-blue Blueberry insert was never an option that was formally offered by Rolex from the factory; however, the same could be said about many genuine service components. At the time, Rolex was not the vertically-integrated manufacturer that they are today, and contracted out the production of many components to third-party companies. While Rolex never offered the 1675 GMT with an all-blue insert direct from the factory, this does not necessarily mean that genuine all-blue inserts were not pro duced as service parts by their third-party manufacturer at the time.
For example, Rolex never offered the ref. 5513 Submariner from the factory with LumiNova dials; however, should you have the dial of your 5513 Submariner replaced by Rolex, it will be replaced by a later-era service component with LumiNova markers rather than the factory-fitted version with tritium markers. That service dial is 100% genuine; however, that exact dial configuration was not something that Rolex ever offered as an option on the 5513 from the factory.
Rolex has stated that (to the best of their knowledge) an all-blue insert was never offered as an original option; however, they have not yet commented as to whether or not the blue insert was ever produced as a genuine service part and fitted to watches after they originally left the Rolex factory.