Allen Bradley Micrologix
Allen Bradley's Micrologix line of PLCs are the old low end PLCs, meant for stand alone machines or small processes. The 1100 can be programmed using the free RSLogix Micro software.
I have a Micrologix 1100, along with some input modules. I first got into obtaining second hand industrial electrical gear by buying an electrical panel from a decommisioned brewerie. The PLC originally had a password on it, so it took some figuring out on how to actually use it.
I'll upload a guide to getting the password off of the 1100 soon, in the mean time here is a notice relating to the vulnerability.