Anyone know what this number on my M275 doors means?

[jacklegjim]

These were painted over when I got the truck. The paint has weathered away and revealed this number. I’m just curious if anyone knows what it signifies. It’s not related to the serial number.

 

[tommys2patrick]

did you buy it from government or private party? not a military mark I have seen. perhaps it was used by a local fire fighting or forest service etc