A few weeks ago I wrote about how great the 1964 edition of this book was. I was curious if a previous edition would be much different. So I located a 1951 edition, and purchased it. The layout at the club is set in the Transition Era, so I figured 1951 would be great. I ended up having to order two copies (which I was lucky to find), as the first copy was "lost" by the postman. They almost lost my second copy, but through a bit of complaining, and several telephone calls, it arrived today. I was surprised to see that it's physically smaller in size. About the size of a school dictionary, or a family Bible. The thing I found that was vastly different, is that it has fold out illustrations of plants or operations, rather than simple flow chart diagrams. It's wonderful to see these. The one for the By-Product Coke Plant is so detailed, you'd need a comparator to see where all the piping goes. Just a fabulous resource. I got mine on Amazon for $25 with shipping. I intend to order a 1940 edition, and there is a 1920 edition I want as well. The 1951 edition is for sure a must have resource for anyone modeling the Steel Mill industry.