"clip" suggests Moen, but I don't see the clip in the photo.( Does the cap sleeve just slide off??) The piece on the end of the stem is a hot limiter. If your water is very hot, it prevents you from actually turning the shower temp up to full hot ( scalding). The screws on the left and right are NOT adjustments....they are shut-off valves so you can turn off the water to service the valve. They must BOTH be fully open for proper operation of the pressure balance mechanism.
Describe exactly what happens....when you turn it on slightly, to the blue area on the plate...is it HOT?? or NO water?? What happens as you turn it further CCW?? If it is in fact a Moen Positemp, it is reversible for reversed hot and cold inlets.