What exactly is "B stock"?

B-stock items are items originally purchased new which have been returned to the manufacturer by the buyer. The manufacturer fixes what was wrong and gives the item a general inspection to make sure it is in perfect working order. B-stock items should work like new and should look like new. They are sold for a significantly lower price than a brand new item and often carry a manufacturerer's warranty of shorter duration than a brand new one.

B Stock can be what Jerry says. It can also be much much more.... Usually what Jerry described is sold as "refurbished".

B stock can be brand new gear. They have left over inventory of the old model in the warehouse brand new. They want to clear it out. To help lower the wholesale price they shorten the warranty period. Since they are not selling it with the full new warranty, they slap a B Stock label on it.

B Stock can also be brand new gear that did not pass final inspection because there are slight cosmetic blemishes. Electronically perfect, just might have slight imperfections on the chasis somewhere.

I personally am not afraid to buy B Stock, even refurbushed gear.

In addition to the above, I suspect the occasional tout of B stock may reflect a sales person's effort to circumvent a dealer's factory authorized territory, often citing the opened box or slight blemish in consequence, when in fact the goods are as new.