Back in the late 60's and up through the 80's the airline were hiring a lot of former USAF & USN pilots with F4 backgrounds. Their airman certificates were restricted to centerline thrust, and consequently this limiation had to be removed before they went to fly the line. Not a big deal but there was some paperwork over and above the normal checkout and since not all pilots in those early days got type rated in the new aircraft, so the IP had to be careful that the CLT limitation did not slip through the cracks. Wish i could tell you this never happened, but the fact is some pilots made it to the line without this box being checked, only to be found by some FAA inspector doing a route check sometimes months after the pilot started flying the line.
Don't recall the 727 ever being anything but a ME rating.