thats the X/Z 250 PE barrel that has those slots in the fins for the TS style square rubbers. most T model PE barrels i have seen have plain fins with no slots like the RM 250 T and the barrels look exactly the same as RM 250 and the round rubbers just squish in between the fins.
on one of my PE's i thought it had a RM cylinder when it just had plain fins and round rubbers, but more research just told me the early PE barrels were like that. but now going by this topic it looks like the Rm and PE barrels are the same anyway. its still a bit strange as the early PE/RM 250s had different porting and i have port maps side by side to show that from suzuki tech bulletins.
i also checked the RM 250 T parts book and theres definitely no small barrel rubbers fitted as standard like the 1980 PE barrel. they were only optional in the offroad sound kit.