Fast Ratio Box Value?

I need some help kinda' quick & hope some people here can help me out. I have found someone who has a 16 to 1 manual steering box that he is willing to sell. I asked how much he wamted for it & he said he would prefer that I make an offer. I have contacted him for info as to how much free play the box has & how many miles the car had on it, & maybe to get a picture of it. Without being able to get my hands on it to determine condition I will have to go on what the seller tells me about it.

What would be a fair amount to offer for this? I want to be fair to him and me. What have they sold for in the recent past? Any help would be much appreciated. Thanks guys!