Western Electric 300b Tubes - Differences

So, sometimes I see these current production tubes for about $900/pair. Then I occasionally see some for around $400/pair. The less expensive ones come in the older style boxes. Was there a period where WE made crappy tubes? If so, when was that? How can you tell by looking at the tubes themselves.

Cheap:

http://cls.audiogon.com/cgi-bin/cls.pl?accstube&1150737895

Expensive:

http://cls.audiogon.com/cgi-bin/cls.pl?accstube&1149506422