superb, you have it in one! Many thanks for the loan of your expertise. I had certainly not seen this mark previously - called a 'dashed square' - and the 'R' in the mark is in fact the R of the word ART - now I will know for the future. Apparently, the furnaces were active from 1950 to 1970 only, so pieces are a good find. Of course I don't have an answer to the 'horns' question - and don't now feel so confident about the pipe holder business. Looking again at Ivo's book, I stand corrected, he does include an entry for this factory, but doesn't show the 'give away' lozenge'. thanks again. Paul S.