After researching Camaro jacks for many years I have found that the Camaros made in Van Nuys were issued jacks made by the the Walker Manufacturing Co. ("square" type post with date code stamped near the top of the post). Sometimes these jacks did not have the date code.
The Norwood Camaros were issued jacks made by the Universal Tool Co. ("keystone" type post stamped "UN" on the up-down lever and with date code on the rivet head). The date coding on these jacks started in "early" 1967, not the Fall of 1966.
I also have seen 67-69 Camaro "keystone" jacks made by "RH INC." but not that often with the date code near the bottom end of the post near the seam. These RH INC. "keystone" posts will NOT fit in a UN "keystone" base.
There is a lot about 70 Camaro jacks (both types) on the NastyZ28 website.