Topic: Clarification on early jacks

[macdude67]

I see in the MCA rules that 64.5 jacks use a corse thread. I have a jack that pinches the welded seam under the rocker to lift up the car. my jack does not have a corse thread but is dated 4E AD. 4 being the year and E being May. What does the AD mean I have seen this on several jacks of different years. The stamping is on the square nut that the screw goes through on the side that has the 13/16 head to adjust the jack. I have seen other datings on jacks on the base plates.