In turn the main source of navigation information came from mission control using least squares. A source on that would be nice too!

I can't make heads or tails of the assembler listing either. The specific thing I would look for in the assembler code is the division operation which is required to find the Kalman gain. I don't see it.

But, the anecdote about the Kalman filters use in this setting is well-known. (E.g., search for "Apollo" in http://ieeecss.org/CSM/library/2010/june10/11-HistoricalPers...)

The amazing thing from my point of view is not the implementation. It is rather that the theory, which was quite novel at the time, was only understood and published in 1960/61. To have it used in a flight system, and indeed a manned flight system, only 8 years later is really incredible.