Positively no apology necessary Abe.

I'm certainly no expert, but in general consider the main difference between 604's and 605's is that the 605 trades a few db of sensitivity for a bit tighter coherence/phasing between the HF and LF sections. The shorter magnet/motor structures of the 605 naturally put the acoustic centers of the moving assemblies closer together.

I've read that 604 production was stopped while 605's were in production. I doubt this is true for the entire production span of the 605 as i've seen catalog pages advertising 605B and 604E simultaneously.

Some points to ponder:

Is there a significant audible difference between 604 and 605?

Is this(phase coherence) why the Beatles preferred it over the 604?

or

Was the cost/price difference truly the most decisive factor for users of a 605 vs. 604?