Some food for thought with the different types of transistors. This book gives a test to ID transistors on pages 14 -15. The test was developed to determine between Point Contact Transistors (PCT) or Alloy Transistors (AT).
The PCT being a 3 junction device with a PN hook in its collector It will have a negative resistance when the collector is "reversed biased". Actually the collector PN hook is being forwarded biased. Look at the structure.
Dr Early defined the 'early effect' which is the base for the negistor operation. Let's take a look at that.
Roger on TRB nailed the description of the PCT operation and then built the circuit being discussed to test his theory. The oscillator sang! Some one blindsided him with the question, "did you try a regular transistor?". He tried a negistor and the circuit sang! Sadly it did not disprove his explanation but was perceived as doing so.
Some times we need to not compare apples and oranges but fail to see that is what we are doing. One of the TRB members has declared a PCT circuit will work without forward bias. Mr Gernsback says while this is true adding a little forward bias will improve the circuit operation. My test circuit worked without bias. When I added a little bias the output picked up and the test was discarded the same as Rogers.