I still stock plenty of the 4-prong jacks and adapters, primarily for sale to collectors. They were phased out in 1973 in Pennsylvania, and in most other Bell territories. Modular jacks came into play as the norm in 1974. Most independent telcos followed suit almost immediately.

The fact that the phone jack is round indicates that it was made by Western Electric (Bell) so I'd venture to guess that the house is older than '80s vintage. Of course, with the quality of the installation, it could also be a case of "Yankee thrift" where grandpa ripped it out of another house and reinstalled it. That certainly would be a first. [Linked Image from img116.exs.cx]

Ettco cable..."Ettcoflex".....I sure ran plenty of that for sure in the 70's and 80's. It wasn't bad stuff at all.

---Ed---

"But the guy at Home Depot said it would work."