yes i have a feeling that's what it is - they probably have piles of these 561b diodes or boards already made and now no one wants them anymore, and soon enough people won't want the 561cs either it'll be the 301bs or whatever. ha ha ha. a friend was considering purchasing these boards off ebay, 2x 308 boards for $150 euro ... i think they are the wrong type and told her i hope she hasn't already purchased ...
@chuckduck i really look forward to following your progress - it will be interesting to see if there is much difference between the 2 sides of your tent. i guess it'd be hard to gauge unless you were monocropping the same clones or something, and there will be quite a bit of overlap near the center. a lux/par meter will be interesting to see as well.
either way i'm sure they both will produce great, so i guess you can look at it like you paid full price for the lm561c and got the lm561b for $17.50 a board... not too bad! maybe i'll ask him if he'll sell the 561B boards for $20 each
after seeing some par numbers hopefully