So I've been wondering what this hive mind would consider the bare minimum of data required in a double-barrelled shotgun sales ad.
No bare minimum of information. I just adjust price accordingly. I bought a local Greener on GB with terrible pictures from an uninformed seller for $500. The seller had gone to a shop and been told it was worth $5K. It ended up being about a $900 gun with good photographs and a relatively informed description. I was happy with the overall transaction(s).
Point being, there is always a price point at which I am willing to gamble, and I will never pay anything approaching a retail or even wholesale price for something with inadequate information and photographs.