Could it be trim position markings as mentioned by Al Fentanyl?
A strong possibility indeed. Back in 1985, the RAAF had an incident in a Viscount of No 34 (Special Transport) Squadron during a training touch and go at Canberra. The pilot undergoing a type rating was making a practice three engine landing with the "dead" engine set at zero thrust. The rudder trim knob on the Viscount was (I think) similar to the King Air. That is, a round knob with the number of units of trim displayed up to the maximum of eleven units either side
In the Viscount, each rudder trim number had a a vertical indice of the same size next to it. For example, the trim reading could show number 9 but the small indice immediately adjacent to that number could make it look like 19.
Before final approach, the PF was briefed for an intended all engines touch and go. This included the PF would not select ground fine but keep all four throttles against the idle stops like any other landing until the instructor had centralised the rudder trim, reset the elevator trim for takeoff and retracted the flaps to the takeoff position. Those actions completed (about ten seconds max), the instructor would tell the PF to apply takeoff power on all engines and complete the takeoff normally.
Initially, everything went as briefed - or so the instructor thought; including the rudder trim being wound rapidly back to neutral. Shortly after liftoff on all engines, the PF muttered something about the rudder trim. The instructor looked down at the pedestal where the rudder trim in the Viscount was situated, and was startled to see he had inadvertently wound the knob to ten units instead of zero units. The problem being the indice and the number zero looked like zero units. However, because the instructor was looking down and to his left at a slight angle to see the rudder trim knob which he had intended to be neutral rudder trim, it had been inadvertently set to 10 units. This may sound confusing to the reader and perhaps a photo of the Viscount rudder trim knob should have been included. The whole point of this post was to show how markings of the various units of rudder trim on the Viscount and possibly the Kingair, could easily cause momentary confusion.
The lesson learned from that incident was it was not good airmanship to complicate things by turning a practice asymmetric landing (albeit using zero thrust on the "dead" engine) into an all engines touch and go. Put bluntly, the instructor was over-confident in his own ability to handle a busy situation. The instructor is busy enough as it is. He is not only watching the landing but has the extra work involved in looking down at the pedestal in order to reset flaps, plus re-setting rudder and elevator trims while at the same time relying on the PF to keep straight down the runway centre-line and lift off at the correct speed.
One can readily understand how a quick downward glance at the rudder trim setting in a King Air may not be enough to ensure it is in the correct position for the task at hand. In the case of the Viscount incident, the writer pleads guilty as charged Your Honour..