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Not sure if it was a blanket replacements of select components or more of checking and verifying everything is 100% operational and repair/replace as needed? It could also indicate that in 2009, it was upgraded to the USMC bolt on MAK Armour and red dot ac.
check out this thread:
https://www.steelsoldiers.com/threads/hmmwv-serial-year-of-manufacture-list.165800/
Your 187303 looks like maybe in the 99-2000 range?