Rob, I have seen other 67 NOR jacks that have a date stamp on the rivet as subsequent years, so maybe this was yet another supplier working to a similar trapezoid design? Let's try and get more 67 info.
Yes, we need more 67 examples either side of 05, both NOR and LOS
On the subject of suppliers, I have read posts by both John and Kurt that suggest there were multiple base suppliers, but not necessarily multiple jack suppliers.
In fact, it may be that there was only the two jack suppliers, one punching out the trapezoidal design that went to NOR and the other punching out the square design that went to LOS, neither of them making the base.
It may also be that considering the safety requirements for such a piece of equipment, that a plant [and the design] needed to be 'certified' in some form or other.
Minimal tooling/assembly is required to punch out bases, there is a lot more tooling and assembly required to punch out masts and ratchets that also conform to a safety standard.
