My Centurion's SR stem has a couple of markings. I see "5355-logo-H-76" and below that in bigger font "AX-80". I don't know which one is the date code, the 76 or the 80. The back of the Weinmann centerpull brake calipers has "1234567890ND" in a circle and has the code I-78 in the middle. The DiaCompe brake levers, which btw, did not have any "suicide" extensions, did not have any date codes. By the date of the brake calipers, the bike seems to have been made in 1978 or later, and no earlier than 1976. The seat post diameter is 27.0mm or something close to that.