These millstones are from an old paper factory in Drammen, constructed as a sculpture/fountain along the river. They were used to mill wood or other substances for the production of paper. Drammen had a huge paper industry back in the days.
I also went to a Salvation Army Charity shop/thrift store today in search for a little item I need in my kitchen. I didn't find it, but I browsed through the shop and I found a sturdy Manfrotto 055xProB Tripod and 804RC2 Head mounted on it. I grabbed it and payed about £20 - $28 - €24 for it. A great bargain. I have the same tripod but not the pan tilt head. If I only bought the head for that price it would be a bargain. Now I have the option to choose between that and a ball head. I'm very happy with my find for today!