Some years back I was corresponding with J. B. Norwood. He mentioned that phrases like "after arrival" in train orders were sticking points with the employees and their union. This is a perfect example why.
Note the time, 5:41pm. Without the "after arrival" language, the Operator at Chama will have to hang around or return later, earning overtime or a "call out" (a minimum amount of pay for coming in during the off-hours). But this order allows the operator to go off duty.
As a result, at least for a while operators could claim a "call out" every time the "After Arrival" language was used in a train order.
I don't know if the arrangement was still in place in 1951, but if it was, Trotter would get paid even though he didn't come back to issue a second order and clearance card.
JAC