Complex sentence: Fender adopted a two-letter dating code in 1990, and the code can be found on the Quality Assurance label, inside the cabinet, sometimes located on the bottom, next to the reverb tank, sometimes on the side.
Split into simpler sentences: Fender adopted a two-letter dating code in 1990. The label is often located on the bottom next to the reverb tank, sometimes it is placed on the side.