If within the discussion period of this list, when did mechanical reefers enter service? Assume since passenger cars began using mechanical air conditioning in the late 30's that reefers would have been soon to follow or did they precede passenger cars?

The discussion of roses being shipped via reefers prompted questions, other than the obvious labor intensity and icing delays of the iced cars, what are the pros and cons of the ice versus the mechanical cars. As I know only of flowers being shipped in iced reefers, assume that humidity was a concern.

Thank you,

Evan Leisey
Bennett, CO