That's not unusual, since Jim Lansing was the head designer of both outfits, first at Altec, which eventually became called Altec-Lansing, and then JBL. The drivers are very similar and since they were pre-T/S all the boxes they went into were empirically designed. With some tweaking to account for the differing specs of different drivers there's a lot of interchangability options. The main difference is that the older Altec designs tended to use Alnico magnets, while the later JBL drivers tended to use ferrite, which came into common usage only after WWII.