These initially belonged to someone who worked at some Chevron offices which were closed at some point and subsequently had housing built on the properties. After he passed, they fell under the ownership of his son, whom I purchased the terminals from.
According to Wikipedia, they are the original IBM 3270s, the IBM 3277 Display Terminal Model 2, circa 1972. They were "dumb" terminals that were designed to communicate with IBM mainframes. Please correct me if I am wrong, but they came with the earliest of IBM's Beam Spring keyboards. A working terminal from Wikipedia:
Sorry for the potato pictures! I am actually away and had arranged for the terminals' owner to drive up to my house and drop off the computers. I'll be returning in a few weeks and will spend some time cleaning up the terminals. More pictures to follow then!
Pictures of the keyboards:
Some other non-keyboard-related photos: