Just to add some corroborating evidence for the YWW dating codes for National Semiconductor during the late 70's, below is an old 69SD5 from a data entry terminal for a Burroughs TD-730. These were made in the late 70's.
[ATTACH=full]211763[/ATTACH]
The board itself has the date code "7834" which is 1978 week 34. So we can expect that dates for the components on the board would be tightly linked to the same time period. And indeed there is an National Semi chip on this board, the gold one on top.
[ATTACH=full]211764[/ATTACH]
the date code of the board, 7834:
[ATTACH=full]211765[/ATTACH]
The NS chip with date code 826:
[ATTACH=full]211766[/ATTACH]
The only way to read the date code of the NS chip so that it is the correct time period for the making of this board is YWW, thus 1978 week 26.
Again, what I think this means is that the chips on the ESB helmet board were swapped out well after ESB was released, probably in the summer of 1981.
