the parts associated with the accumator piston are as follows:
-F320203200 snap ring x2
-91A2812801 seat, accumulator spring x1
-0550035023 o-ring x1
-9122826300 spring, outer x1
-9122816400 spring, inner x1
-9122815201 piston, accumulator x1
-0550035024 o-ring x1
-91A2821201 plug, accumulator x1
These are all the parts shown in the piston accumulator assy in the control valve for the P5000 in your serial number range.