I'm sure there were SOME 7-segment displays before 1970, but 'Neon' "Nixie" tubs with nicely formed numbers were most common.
The first digital clock I built for Broadcast stations in 1970 used the RCA "Numitron" which had filaments in a 9-pin vacuum tube envelope. They were driven by the SN7447s. They looked like this:
Actually they looked better in a dark cabinet...
A friend and I made a few dozen displays with plastic segments embedded in dark "Bondo" type auto body filler. We made 2-foot long strips, and sawed about 24 sections off, polished the fronts a little, and embedded small incandescent bulbs in the back. That was Broadcast Clock V2, followed by the Recording Timer, where you could see the running time from when you pushed "start" on the cartridge tape machine :-)
Digital Logic. Wow. I was very temporarily the State of the Art in my field. My FET stabilized crystal oscillator with schmitt-trigger output to digital was published in Electronics.
Boy, is that stuff obsolete
I'm trying to stay at least somewhere ON the obsolescence wave