METAL STEM & Screw thro bowl
About the same time as Dr Kirsten , George Ash in Washington DC was working on a metal shanked pipe. In 1938 the Ashcraft Lifetime Pipe was launched. Like all the aluminium pipes, the War stopped production for the home market and in 1946 it restarted.
This time there were four models, one with a briar bowl with metal insert, which can be discarded and the pipe smoked as a briar bowl. Another was an all metal double shell bowl. The inner shell is removable for cleaning. The two shells do not contact each other, a wooden ring separates them. The bit is of vulcanised rubber, the bowl has 7 holes in the bottom. An Oom Paul version produced Nov 1946 “Chin Rest” added an extension to bowl of Duoplex, and use curved bit.
This example is the plain briar bowl. Unsure as to whether this could have had a metal liner to the bowl. The screw through the bowl engages a thread in the actual bowl so the bowl can be removed from the pipe without a screwdriver being needed
Check out US Patent D144,346, April 9 , 1946 and also D144,345 April 9,1946