If it's an issue field jacket, it was treated with Quarpel and can be re-treated if and when needed. You can dig the info up on the 'net by searching on Quarpel - I'm pretty sure that it's available retail (but under some other cutsey brand name) nowadays. Quarpel treatment stands up to many (~15) full Quartermaster laundry cycles, so it's quite durable.

HTH,

Tom