The 2561 NuTone Master Station was manufactured in 1973 and this is the first time it has ever been repaired.
In all of its Avocado Glory this 2561 is truly a nice unit. There are different chassis versions for the 2561, this is a "J" chassis.
As noted in the service manuals chassis beginning with the "G" series use all silicon transistors (original units had Germanium transistors) and silicon diodes.
The FM tuner module is also a newer design starting in the "G" series and it is not interchangeable with the earlier units.
This 2561 only need to have its capacitors replaced along with a "new" volume control and a Tuner alignment.