With Nichia,
It depends on how many LED's you buy. The bag them in bags of 100 and 500. If you buy 20 LED's you will get whatever the bin is from the bag that they have open. If you buy thousands of them, you may get bags of different bins but then again maybe not. I have bought 5000 at a time and they are always of the same bin and lot.
Regarding the S, in the number the S after the b1 or b2 is an indication of brightness rank with the S being the highest color rank abvailable in the states. The b1 and b2 refer to color rank. The BS ( no pun intended) in NSPW500BS refers to the type of leads; in this case PCB stops.
Mike,
I believe those LED's were mentioned a month or two ago here on the forum. If they're the LED that I'm thinking of, I believe the beam angle is narrower than the NSPW500BS and the actual total light output will be less than the Nichia. The S rank Nichia has a typical output of 8000 mcd with a min of 6800 and max of 9500 and this is with a 2X theta 1/2 of 20 degrees.
- Don
EDIT: Regarding the binning of Luxeons, as I understand it, Lumiled does mark their bulk packaging with bin information. Future does not sell to the casual user by bin identification and their own part numbers and labeling do not contain the bin information. If you buy in bulk, you can determin what bin clasification you have received but you can't order or request product by bin classification. I do believe if you are a large player, bin selection is a possibility.