I didn't noticed the dirt on the face of pipe. As I said this stove was bought by my daughter who lives in Beaufort, S.C. I haven't seen the pipe/and stove personally only from this picture. If there is dirt on the pipe, I am sure my daughter would have cleaned it off because f the younger children. I did say that my granddaughter was freaked out when she seen a tall black man w/white bare feet and horns on his head walking in her bedroom. I later found out that the horns were hair that was napped on the head, and ashes on the feet to give a white appearance. This spirit didn't communicate with, or try to harm anyone. So, I feel it was a Residual haunting taking place there. As far as the imprint on the stove pipe, I am still wanting opinion. The stove pipe is not connected to the wall, and the stove is like an alter for my daughter candles and prayer items. When I found more out since there are a few people taking interest of this picture. I will keep it up dated. Phil W./Oh.