I often see things in the pile and puzzle over what to do with them. The big pin that makes up part of this piece is such a thing. It sat there for years and finally I felt it was like a pin that coupled carriages together so what better use than to upgrade it to an actual engine. Some of the other pieces were just nearby so it really is a collection of bits that spent time together outside. It certainly is a heavy piece but sort of fun and cool too!