[cctalk] Scada computers and remote terminal units

Greetings, Been a long while since i have posted in on here. I usually discuss my pdp 11 and vax systems. I have decided to pivot my career to scada syatems. The company i am with has some interesting stuff that goes pretty far back. Our custom in house tech is a plc pump controller with a radio connection for data logging and control. Pretty cool, 8051 based, with a version of basic in rom that has scada functions added. The backend servers are just linux systems, although in a modular backplane for easy replacement. I have not read much about this tech outside of what we have in house. Are there other historic scada system computers or technologies that are similar, easily found on ebay for example? Ive seen some mention of old allen bradley stuff, but not much notes on how it would be used remotely in the field, as a remote terminal unit. Any suggestions are appriciated, trying to read more into scada tech outside of my company's tech. Thanks, Devin D.