Look at the part numbers of the PSR. 01143. Been that way for over ten years (maybe 15). Now there are some extensions like s7, ws7, ws9 etc. Probably different piston materials/design over time. Like I mentioned before, I really don't think RB has had a new sleeve design since Rody left in the mid 2000s. Now they have changed names, packaging, coatings, anodizing, heads, etc. But from what I see the same base PSR has been used for years in the S7, WS7, WS9, F11 line and C5/C6, B10, B11, BX/R etc.

Lots of different revisions in the crank and bearing sizes also.

You see many many more engines than I do, I am just going off of part numbers.