Nailed It!
Finally got around to looking in Dolf's book, and watching the video again. There are more than one still images that must have been shot the same day as that video, at Remington's Bridgeport facility. The still #122 on page 108, is clearly the same area and time frame. The fellow center, in the overcoat, also appears in #125 on page 111, where Dolf's caption suggests that A.I of O., Major E.E. Chapman, may be the officer on the right. The three men in image #125 are clearly shown in the video, and you can see virtually the same moment that the still picture shows, taken from an angle just outside the film camera. I am guessing that the gentleman testfiring in the end, and pictured on page 115, is the Mr. Best who is shown on page 107. He was apparently the "works manager" at the Bridgeport plant. Very cool stuff!