Sam checks Edie's pulse on her neck using his thumb. The thumb has a pulse of its own, so it is possible to get an inaccurate reading. One of Sam's degrees is a medical doctor, so he would know that.
Byron considers hiring Twiggy for the modelling shoot. However, Twiggy's modelling career did not begin until 1966.
In Karl's apartment the stereo equipment is of much later vintage. The amplifier, preamplifier and tuner are Accuphase units that were made around 1975.
In Edie's apartment, the television is of much later vintage. Solid state sets did not appear until 1967 and the Panasonic set is of about 1975 vintage.