Thanks for the feedback, glad, that everything is okay.
Someone named them as "Bob-Widlar-Memorial-OpAmps".
![ThumbsUp :-+](https://www.eevblog.com/forum/Smileys/default/icon_smile_thumbsup.gif.pagespeed.ce._JElyJQqdB.gif)
They are uA709AHM, the red dot comes from Rohde & Schwarz, they have selected them for some (to me) unknown paramters.
![](https://i.imgur.com/z62SDly.jpg)
I have 200+ pieces of them, more than enough for a lifetime.
If you are interested in some of them, send me a PM. :-)
Presumably because they either are matched to a specific characteristic, or because they are outside of the requirements... do you know if ones used in their TE are dotted or not?
The Telefunken VF14 used in the Neumann U47 microphone was ruthlessly selected at Neumann for low microphonics and a number of other things, thus became a VF14M. This was a process that
the entire production of VF14 went through. Those not fulfilling the required performance demands were shipped back to Telefunken, and used in a simple Allstromempfänger. Today, audiophools willingly buy NOS VF14 (i.e. Neumann rejects) valves to put in their U47 microphones. Which is not a very clever thing to do, if you want to preserve the microphone as it should be.
At the end of the VF14 production era Neumann noticed that the acceptable portion of new batches started to shrink. They did some complaining, which was stone-walled, and then resorted to more cunning tactics; all rejects were marked with a small, somewhat hidden paint dot. It should not come as a surprise that they found the little dot on several valves in the next shipment.
Thus ended the VF14M era.