I know Trimlines had the "big" modular cords from 1965 on, but when did modular cords come out? I remember we got new phones as a kid in 1974, and the handsets were "modular" plastics with hard-wired cords shoved into the notched hole (really). I remember looking at the odd shape of the hole the cord went through, wondering why it wasn't round. I don't think Ma Bell actually started installing fully "modular" phones in homes until about 1977. This was pretty much the death of the phone installer, because then the "Phone Center Stores" came into the malls, and they would give you these little phone jack converters that snapped over your 42A connection blocks, and you would pick up your new phones there. I know Michigan Bell actually "retro-fitted" Princess phones in the late seventies (why, I don't know), my grandmother had a green princess in her bedroom, and the phone man came in with his "notching tool" and converted it to modular. He then wrote an "M" above the area code on the number card on the phone. I don't know why this was done. Any thoughts about modular and when it was first used? I've heard everything from the mid-sixties to the late seventies.
I have read on Paul Fassbender's "Old Telephones as Entertainment" website (www.paul-f.com), that Western Electric began offering modular phones in 1972. The most interesting model 500 phone I have is a black ITT manufactured in July of 1989; it is a hardwired, but uses a modular handset with the hardwired handset cord shoved into the modular opening. ITT apparently stopped manufacturing hardwired handsets around 1984, according to Daniel's "History of 4th Genenration Telephones" (http://members.dslextreme.com/~zuperdee/index.html) but continued to manufacture hardwired phones.