As far as I know all of the stuff in the sale has a minimum sales price, which is the least the MoD will take for it. Remember Withams don't own all the stuff they sell, most of it is owned by the MoD. The way to tell is by looking at the stickers with the stock numbr on, e.g. SV688, T1234 etc. If the sticker is blue it is owned by the MoD, if it is red Withams own it. If the bids are close I think they let the item go, if it is way off then they hold it back untill next time.
Chris