I bought a Honeywell RTH221B Thermostat to replace my the old 50's thermostat in my parents house. When I disconnected the old one, there were only two wires, not color-coded and no letters or number or anything on the device itself where each wire was connected. Where do these two wires connect on the new thermostat - my choices are Y or G on the left side, or Rh, Rc or W on the right side. There is already a tiny connector between Rh and Rc.

Assuming it is a heat only system, it should be R and W on the old thermostat. Leave the connector on and connect to either Rc or Rh and W. Polarity does not matter, its AC powered.