Spy Car
Head-Fier
I'm a bit confused. My research indicates that code 280 is Raytheon MFG code and those tubes look like Raytheon tubes. 312 is Sylvania MFG code and the mica structure looks unlike any Sylvanias I'm familiar with.
When I look up the MFG code (no expert here) I'm also seeing Raytheon listed for my Zenith tubes.
I just scored a real "new" vintage NOS Tung-Sol Jan 5998 from a local tube wholesaler. Stoked!
Bill