These photos seem to be "post 1960" to me. Among other clues I notice
that in the last of them there is a guy wearing what looks to me like a
fairly modern "safety vest" (yellow/orange).
I'm not complaining - just asking the question "probable image date?".
If any of you haven't seen it ... search for images of Jack Burgess's
excellent model of an early weed sprayer. I think you will find them
easiest if you look in recent (last year or two) PCR convention contest