While in USMC attending Sea School, in 1958, at MCRD, in San Diego, CA, we all took chow at the Drill Instructor’s Mess. We were marched in formation to the covered passageway, outside the Mess' hatch; where we stood "at ease," prior to entry.
One morning, we (the Marines in our formation) spied a young recruit, double-timing, with a M-1 rifle (at port arms), around the periphery of the Grinder, located to our direct front. Simultaneously, a "Brown Bar Lieutenant” walked through the Mess' hatchway, and proceeded to intercept the “green recruit.”
The young recruit had obviously yet to learn how to render a proper, regulation rifle salute, with his weapon. The 2nd. Lieutenant ordered the recruit to halt. After “chewing-out” the dismayed recruit, this officer taught (instructed) the recruit to salute, using Present Arms, with the rifle.
Meanwhile, a full bird Colonel appeared in the hatchway. The Lieutenant, having not seen the Colonel, proceeded to order the recruit to salute him 100 times, with the obligatory: "Good morning sir!"
The Colonel watched this one sided spectacle proceed through – 20 repetitions, and then he interrupted this curiosity. After returning the startled Lieutenant's right-hand salute and greeting, the Colonel complemented the junior officer, for assisting in the training of the young recruit.
Whereupon, the Colonel told the Lieutenant that officer's always return salutes. Following his instruction, the Colonel ordered the Lieutenant and the recruit to "Carry on, starting at 1!"
Our formation was then marched into the Mess Hall. While we ate chow (with a chuckle) we could hear "Good morning sir! "Good morning recruit!" echoing from the passageway, outside the Mess Hall.