Nancy Wood BF3 Proportional Counter (ca. early 1950s)
This neutron detector was produced by the N. Wood Counter Laboratory in Chicago Illinois. Nancy Wood began manufacturing detectors in the Manhattan Project at the University of Chicago. She started the N. Wood Counter Laboratory in 1949 and the company is still in the business of manufacturing radiation detectors.
The tube is approximately 5 inches long, 1/2 inches in diameter, brass walled and filled with BF3. The active length of the tube, the right end in the above photo, is probably about 2 inches.
The model number, marked on the wall of the tube, is G 2329 (the last digit is somewhat uncertain). The company used a G designation for their brass walled enriched BF3 counters. At least since 1958, the company has used a different type of model designation (e.g., G-10-20) with the first one or two digits describing the tube's diameter. The small diameter of this tube would warrant a "5" designation in this system. For this reason, I am guessing that the tube was produced in the early 1950s. This is pure speculation however.