Electure:
Yes, this is '05 NEC. My understanding is that the six-disconnect rule existed long before this service was likely built, otherwise, why would split-bus equipment have existed?
I didn't actually go back and look up the lineage of these two Code sections.
Pulling off the shelf at semi-random, the '71 NEC, I find language substantially similar to 408.36(A) in the '05 NEC, with an exception that would seem to apply to split-bus equipment:
384-16
(a)Each lighting and appliance branch-circuit panelboard shall be individually protected on the supply side by not more than two main circuit breakers or two sets of fuses having a combined rating not greater than that of the panelboard.
Exception No. 2: Individual protection for lighting and appliance branch-circuit panelboards is not required where such panelboards are used as service equipment in supplying an individual residential occupancy and where any bus supplying 15- or 20-ampere circuits is protected on the supply side by an overcurrent device.
This exception would seem to allow a split-bus panel but not a main-lug panel as shown in the photo.
Here's 408.36(A), Exception 2, from the '05 NEC:
For existing installations, individual protection for lighting and appliance branch-circuit panelboards shall not be required where such panelboards are used as service equipment in supplying an individual residential occupancy.This would seem to grandfather this installation, although the '71 NEC does not seem to have permitted it. When it may have been legal to install such a panel as service equipment I do not know. I do know that AHJs around here will grandfather a split-bus, but not one of these.
(BTW the 6-disconnect rule is in the '71 NEC.)