Alexban - good observation.
I confirm the same! I have also noticed that on all the 737's (right from the jurrasic's, classic's & NG's) - all have 'some' difference between the left & right trim readouts. I have noticed it on brand new A/c's also, just delivered from Boeing. Earthmover - you must have flown a super-rigged A/c !
I remember - as a F/O, we used to reach over to set it as per the Capt's readout, least we tick off the old man !!
The explaination I have gathered over the years is:
All calibration is done as per Left side trim readout. If you look even more closely - you will notice that there is even a difference between the length of scale between left and right. i.e. length of scale from 1 to 15 units, is longer / shorter than the other. (now my old age has made me forget which side !!). This is easily done by making small marks on a piece of paper and comparing left and right!! There is also a difference in length in of the opening in which the pointer runs. Also decals are different.
The engineers need to get the left and right trim wheels between a certain MM value during calibration, and since I believe this is a very cumbersome process, most guys just make sure its withen the value, and not perfect ! Can also tell you, that the DFDR pick-up is from the left side, but not necessary the same as what the pointer shows.
Have questioned a few Boeing test pilots and safety pilots, but did not get favourable answers.
X-feed. I am not aware that 'only' different manufactures make left and right trim wheels. If it is true, then its a VERY good question, and then I'm sure it will have a very GOOD reason.
Sorry for the long post.
4MONU