It's not on top on an ISL - it is kind of buried.
The engine data plate is located on the top side of the gear housing, which will be in the lower right quadrant when viewed from the access door at the rear of the coach. If the engine data plate is not readable, the ESN can be found on the engine block on top of the lubricating oil cooler housing. Additional engine information is on the electronic control module (ECM) dataplate.
ESN - Engine Serial Number
For other Cummins engines and their data plate location, see:
https://quickserve.cummins.com/info/qsol/service/find_esn_tip.print