I assume high telecom??
What was the purpose or style of square silver blocks on front and back

Looks kinda like a custom or prototype breadboard, could just be the style of the board though.
¯\_(ツ)_/¯

Should be high Telco

_________________
Here to learn more so I can recycle more
My grades are my own opinion and not an official grade from Boardsort

It's an alternative type PCB to a "perf" board and/or breadboard. And also a straight out wire wrap PCB. The wire wrap board requiring wire wrap sockets. It can be used for home projects. Experimental boards. And even final production. Same concept in making connections. Soldered individually point to point using extremely thin wire. In your photo is a small example. Look at the green edge connectors. Top or bottom of PCB. You can see small wires have been soldered in place already. YOU have a PCB that has been populated already. Most likely had been wave soldered. And is now waiting to be "hard wired" by a tech to complete all the connections. Yes. Done by hand. BUT. The PCB in the photo has not been completed. Most likely over run from production.
Here to learn like everybody else. I would call it High Telecom.

Interesting piece. Definitely a breadboard like others have said. I haven't seen one of those since i was in college long ago. But the form factor of the card also seems to be a Telco blade for commercial / enterprise equipment. My guess is that its Telecom prototype / lab equipment.