Delco was a subsidiary of General Motors which developed car electronics and radios. They also supplied tubes under their own brand.
As far as I am aware they did not have tube manufacturing of their own, so these were rebranded tubes from the major suppliers.
As with most tube boxes the earlier one had beautiful logos :
And got simplified over time:
The latest boxes had the most bland design:
I found this tube box branded General Motors Parts Corp. Not sure if that was part of Delco or if this box is from a time prior to the formation of Delco.