[Amps] 6146B vs. W

[W6NQ]

I have a little practical experience with various "B" & "W" variations.  
The GE 6146B and ECG-Philips (old Sylvania) 6146W tubes work well in the Kenwood HF transceivers, and have comparable life spans.   This has been verified by one Kenwood service shop which has used hundreds of the ECG tubes over the last several years.
The generally available GE 6146W definitely DOES NOT hold up in the same application.  
I would suspect that the GE 6146W may be of the "A" category.

Merit,  W6NQ