"DaveC" wrote ...
These all have the National logo (NS) followed by either "333",
"324", or "336". I presume that they are all 2N devices.

Not a safe presumption. They could be "house numbers"
or even a date code. (Date codes are sometimes encoded.)

Where did they come from? Those numbers sound too low
(old) to be in modern TO-92, IMHO.