I think the relevant CPSC regulation was issued in early 1976 so the altered components appeared during that year. The caliper in your photos is "pre-CPSC". You can see that the quick release lever is a flat blade - must have been responsible for untold man-slaughter and mayhem. The regs also drove the change to the Campy FD where another murder weapon was, so the leading edge was curved away from the chain (away from the frame) to blunt that edge. My 76 Raleigh Professional has the Post-CPSC designs and I feel so much safer.

There is some indication that the 1976 Standard also mandated the plastic reflectors on the front and rear and in the spokes of each wheel. The front disk blocks a perfectly good view of the head badge and the rear disk protects the underside of the saddle from flying debris. If you get bored some time, hold your reflected front wheel between your hands (grab the axle ends) and spin the thing. Then contemplate out noticeably unbalanced the wheel is due to that chunk of plastic, even at such a low speed. Funny, I looked around and all my reflectors seem to have disappeared #:^) I'm able to avoid riding those bikes in the dark.