Since starting this thread, I bought several AC Gilbert booklets that had some info on TruModel. One is a 1927 Kelmet Catalog that shows most of the pages from the TruModel booklet that I have had for years. It looks like Kelmet had an agreement with TruModel to sell the hoist, the Derrick and the trolley unchanged from the TruModel Toys. I am guessing the later, AC Gilbert bought out Kelmet and TruModel. Both products were too costly for his business plan. He did include the tipping bucket and the clamshell from TruMode and the fenders, hood and steering from Kelmet. He had the hoist redesigned to use Erector parts and cost a great deal less. He dropped the Kelmet name, but used the TruModel name for the Erector sets that were sold through Sears and Roebuck. With the onset of the depression in 1929, he dropped about a hundred items in the various sets to reduce costs. He also stopped using the TruModel name.
That is the story as I have been able to piece it together. I would be grateful to anyone that can correct any errors in that story. Thank you.

Yesterday, 9/25/2024, I received another TruModel Derrick from a man in Tempe Arizona. Thank you Noah. I bought it from him because it included the A frame that I was missing. That addition almost completes my Derrick and hoist. The only thing missing is the trolley. If anyone has a spare, I would like to buy it. Thenks.