that the 737 was a "certified" aircraft, and so was supposed to be trimmable at any speed within the flight envelope.
unfortunately, that is not quite correct. There is an assumption that the crews can cope with an out of trim case at all times, e.g., there is always sufficient authority of the elevator to cope with an out of trim stabiliser, but reality is that is not what the rules actually require. The protection of the certification standard gives a partial coverage for out of trim conditions, of a 3 second error only in the trim at all speeds within the normal envelope effectively.
Point taken.
Was meaning "the trim was supposed to be moveable"...