If one looks closely at the labels themselves, you can see that the original order was C-A-B.

it strikes me as odd they would elevate the coal damn near to the top of the building to transfer it into the building. The amount of energy to lift 100 tons of coal (I seem to recall that was the amount used on a daily basis at one point) must be considerable, rendering the process itself somewhat inefficient.

I imagine there were design issues involved where the plant might not have been laid out with the eventual volume of coal in mind when it was built. Maybe it _was_ that way from the start, who knows.

Eventually, the plant was converted to other fuel sources, rendering the coal loading process a moot point. However, the inefficiency might have played a part in the migration to a different fuel source.

Some companies subsidize the cost of the various sodas and other drinks offered on their premises for their employees -- such as MedicSpanker mentioned. I don't think that any true timeframe for the machine can really be established based on the price of soda on the machine. The machines themselves were designed to be adjustable as to the coin mechanism, allowing price increases over the years, of course.

I would hazard a guess the machine is from the later '60s or early '70s.

they've been there since the mid-late 60s, as far as i can tell.

they're LDS465 diesel or multifuel engines, for 2.5 or 5 ton military trucks and 6x6s.