Precision analog vernier dial or standard rotary slide ruler.
Vintage radios can develop minor issues over time. The original manual outlines these common fixes: Radio Shack 12 150 Manual
If you require a literal page-by-page PDF replica of the physical manual for restoration or archival purposes, several digital repositories host these documents: Precision analog vernier dial or standard rotary slide ruler
Fully extend the antenna for FM/WB. For AM, reorient the unit. Move the radio away from large appliances, computers, or fluorescent lights, as these emit electromagnetic interference that disrupts radio waves. or fluorescent lights