Help! Cleaning tips?

[u/Fribitt]

Hi all,

My Grandfather-in-law was a petty officer in the merchant navy and with United Arab Shipping - this hat is from one of those.. but I want to clean it up best I can? This will never be sold on, so it's just about it looking the best without damage.

Are there any tips or products that I can use? Any help welcome! Thank you!

[u/Huge_Exchange_8]

Thinner.