Updated: Jul 20
There is a lot to know about Berns-Martin's inverted shoulder, not least of which being that Jack Martin was the first man to ever sling the revolver upside down at the shoulder; as he did with his inverted knife sheath for the Fairbairn-Sykes blade. This was just prior to WWII in the 1930s. This first image is from Elmer Keith's personal collection and according to B-M catalogs these first ones were made entirely of the horsehide from which the harnesses were made: the harness is actually integrated into the holster.
Jack used an ink stamp on them, likely because the steel stamps he was using (believed to have been cadged from the ship's engine room) for the Speed holster don't make a clear marking in soft, chrome-tanned leathers. Tricky, tricky, the oval mark for Calhoun City didn't appear until the War was over, circa 1950. The 'CS' of course is Chiefs Special and that revolver didn't appear until 1951 or so (exact date here somewhere) and B-M's primary customer, Evaluator's Ltd, received the very first of the Chief's in that year.
As far as we can tell, then, no Lightnings from the pre-War period have survived into modern times; Keith's own from the first image, here is from the '40s (1944 publication below). It is the only known 4" to be made, Martin himself being on record as saying small frame 2"-3" only available. Keith was special to Berns and to Martin because he was their benefactor.
Few would know that after the Elberton GA era that followed the Calhoun City era (that was preceded by the US Navy era) there was an Atlanta GA era. That's because it's most likely that any of these the Blackie Collins produced were marked Elberton; he appears to have been primarily interested in producing his knives with the Berns-Martin mark, and sheaths to match. The same players in Elberton were partnered with Collins in the Atlanta operation, according to its incorporation documents.
Read more in my book titled "Holstory -- Gunleather of the Twentieth Century -- the Second Edition" that is available at www.holstory.com and printed for you/shipped to you in USA.