Chinese Shuguang have produced 12 kinds of 300B in past some years.
I konw 10 of them
300B: the first kind of Shuguang 300B.Carbonized anode. Stop producing.
300B-98: old type. Stop producing.
300B-98B: Carbonized Mesh-plate. Metal base or ceramic base
300B-98C: Mesh-plate and anode sprayed with hydrogen titanium
300BA: copy of WE 300B. stop producing.
300BAW: copy of WE 300B. spring hook filament.
300BC: Graphite anode and ceramic base.
300BS: Globe shape and mesh-plate with metal base
300BS-B: Globe shape and carbonized mesh-plate with ceramic base.
300BS-C: Highest-level and expensive product. Few are found in markets.
Most are ordered by amplifier manufacturers.
Photo:
http://www.diyaudio.com/forums/attachment.php?s=ebdf93373f5c30f6bf932efb0d14320a&postid=359120
