Not to speak ill of your character, but the general thought is a blind auction is bad because nobody knows who is bidding and what they bid. This means that a person could set up a situation where they have someone basically bid against themself. Not saying you would do this, but the potential is there. So I could say, bid 550, and that could be your best offer and then you could PM me and say "just got a bid for 575, can you do 600?" I would think there is a legitimate bid for 575, bid 600 and then all of a sudden I am out 50 bucks bidding against myself.
Just curious, you were fervent about the fact earlier in your bid that this was not a commercial product, that you were building it for yourself, and then you admitted that it was a prototype for a kit, and now it turns out you are selling it. Why are you selling it? Did something go wrong with the design so that you ended up not liking it? Do you just want the money? Or was that the plan all along?